Chapter 8 الباب الثامن The Cellular Basis of الأساس الخلوي Reproductionللتكاثر and Inheritance والوراثة Lecture by Richard L. Myers.

Chapter 8 الباب الثامن The Cellular Basis of الأساس الخلوي Reproductionللتكاثر and Inheritance والوراثة Lecture by Richard L. Myers Translated by Nabih A. Baeshen 1

الروابط بين الانقسام الخلوي والتكاثر
CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION الروابط بين الانقسام الخلوي والتكاثر Copyright © 2009 Pearson Education, Inc. 2

8.1 Like begets like, more or less الذرية تشبه الآباء، قَل أو كَثُر
Living organisms reproduce by two methods تتكاثر الكائنات الحية بطريقتين. Asexual reproduction التكاثر اللا جنسي Offspring are identical to the original cell or organism الذرية تماثل الخلية الأصلية أو الكائن الحي. Involves inheritance of all genes from one parent تتضمن وراثة كل الجينات من أحد الأبوين. Sexual reproduction التكاثر الجنسي Offspring are similar to parents, but show variations in traits الذرية تشبه الأبوين مع تنوع في الصفات. Involves inheritance of unique sets of genes from two parents تتضمن وراثة مجموعة معينة من جينات كلا الأبوين. Most eukaryotic organisms are capable of both asexual and sexual reproduction. Students may be surprised to learn that asexual reproduction plays a major role in the life cycles of many organisms. For example, the unicellular algae Chlamydomonas generates an increased population by asexual reproduction when conditions are favorable for cell division. In unfavorable conditions, the organism undergoes sexual reproduction. This has the advantage of producing a new combination of genes and traits that could be advantageous for survival under new environmental conditions. Student Misconceptions and Concerns 1. As the authors note in Module 8.1, biologists use the term daughter to indicate offspring and not gender. Students with little experience in this terminology can easily become confused. 2. Some basic familiarity or faint memory of mitosis and meiosis might result in a lack of enthusiasm for mitosis and meiosis in some of your students. Consider beginning such lectures with important topics related to cellular reproduction. For example, cancer cells reproduce uncontrollably, stem cells have the capacity to regenerate lost or damaged tissues, and the study of embryonic stem cells is variously restricted and regulated. Teaching Tips 1. Sometimes the most basic questions can challenge students and get them focused on the subject at hand. Consider asking your students why we expect that dogs will produce dogs, cats will produce more cats, and chickens will only produce chickens. Why does like produce like? Copyright © 2009 Pearson Education, Inc. 3

Binary fission means “dividing in half”
8.3 Prokaryotes reproduce by binary fission الكائنات أولية النواة تتكاثر بالانشقاق الثنائي Binary fission means “dividing in half” يعني الانشقاق الثنائي ”الانقسام إلى نصفين“ Occurs in prokaryotic cells يحدث في الخلايا أولية النواة Two identical cells arise from one cell ينتج خليتين متماثلتين من خلية واحدة Steps in the process: خطوات هذه العملية: A single circular chromosome duplicates, and the copies begin to separate from each other يتضاعف الكروموزوم الحلقي الوحيد, وتبدأ النُسختين في الانفصال عن بعضهما البعض The cell elongates, and the chromosomal copies separate further تستطيل الخلية, ويزداد انفصال النسختين الكروموزموتين أكثر فأكثر The plasma membrane grows inward at the midpoint to divide the cells ينمو غشاء البلازما ممتداً إلى الداخل في نقطة المنتصف ليقسم الخلية The process of binary fission is very rapid. E. coli cells divide every 20 minutes under optimal environmental conditions. The antibiotic penicillin inhibits the growth of the bacterial cell wall. Cells can duplicate their internal contents, including the chromosome, but will burst when they become too large for the existing cell wall. Student Misconceptions and Concerns 1. Some basic familiarity or faint memory of mitosis and meiosis might result in a lack of enthusiasm for mitosis and meiosis in some of your students. Consider beginning such lectures with important topics related to cellular reproduction. For example, cancer cells reproduce uncontrollably, stem cells have the capacity to regenerate lost or damaged tissues, and the study of embryonic stem cells is variously restricted and regulated. Teaching Tips Consider contrasting the timing of DNA replication and cytokinesis in prokaryotes and eukaryotes. In prokaryotes, addressed in Module 8.3, these processes are over-lapping. However, as revealed in the next few modules, these events are separate in eukaryotes. Copyright © 2009 Pearson Education, Inc. 4

Binary fission of a prokaryotic cell
Plasma membrane غشاء البلازما Prokaryotic chromosome كروموزوم الخلية أولية النواة Cell wall الجدار الخلوي Duplication of chromosome مضاعفة الكروموزوم and separation of copiesوانفصال نسختيه 1 Binary fission of a prokaryotic cell الانشقاق الثنائي لخلية أولية النواة Continued elongation of theاستمرار استطالة cell and movement of copiesالخلية وحركة النسختين 2 Figure 8.3A Binary fission of a prokaryotic cell. This figure shows the steps in binary fission. Division into two daughter cells الإنقسام إلى خليتين بنويتين 3 5

THE EUKARYOTIC CELL CYCLE AND MITOSIS
دورة الخلية حقيقية النواة والانقسام الفتيلي Copyright © 2009 Pearson Education, Inc. 6

8.4 The large, complex chromosomes of eukaryotes duplicate with each cell division الكروموزومات الكبيرة المعقدة للخلايا حقيقية النوة تتضاعف مع كل انقسام خلوي Eukaryotic chromosomes are composed of chromatin تتكون كروموزومات الخلايا حقيقية النواة من مادة الكروماتين Chromatin = DNA + proteins الكروماتين = دنا + بروتينات To prepare for division, the chromatin becomes highly compact, and the chromosomes are visible with a microscope تمهيداً للانقسام, يتكثف الكروماتين بدرجة علية, وتصبح الكروموزومات مرئية بالمجهر Early in the division process, chromosomes duplicate تتضاعف الكروموزومات في المرحلة المبكرة للانقسام Each chromosome appears as two sister chromatids, containing identical DNA molecules يبدو كل كروموزوم منشطراً إلى كروماتيدياتين شقيقين, تحتوي كل منهما على جزئ واحد من الدنا متماثل لشقيقة Sister chromatids are joined at the centromere, a narrow region وتتصل الكروماتيدتين الشقيقة بالقطعة المركزية, المنطقة الضيقة Chromatin is compacted about 100,000 fold to produce the interphase/metaphase chromosome. If all the DNA in the human chromosomes were aligned, it would stretch for one meter. All of this DNA is condensed to fit into a nucleus that can only be seen with the aid of a microscope. The centromere has a unique DNA sequence involving repeated stretches of nucleotides. In biotechnological applications, artificial chromosomes can be produced that have a centromeric sequence. This chromosome will be properly distributed during cell division because the spindle fibers attach to the artificial centromeric sequence. Student Misconceptions and Concerns 1. Students often seem confused by the difference between a DNA molecule and a chromosome. This is especially problematic when discussing DNA replication. 2. Students are often confused by photographs of chromosomes. Such photographs, such as Figure 8.4B, typically show duplicated chromosomes during some aspect of cell division. It remains unclear to many why (a) chromosome structure is typically different between interphase G1 and the stages of division and (b) why chromosomes are not photographed during interphase (the stage in which chromosomes are typically first discussed) before the chromosomes duplicate. Teaching Tips 1. Figure 8.4C is an important point of reference for some basic terminology. Consider referring to it as you distinguish between a DNA molecule and a chromosome, unreplicated and replicated chromosomes, and the nature of sister chromatids. Copyright © 2009 Pearson Education, Inc. 7

الكروماتيدتين الشقيقة
Sister chromatids الكروماتيدتين الشقيقة Chromosome duplication تضاعف الكروموزوم Sister chromatids الكروماتيدتين الشقيقة Centromere القطعة المركزية التوزيع الكروموزومي على الخلايا البنوية Chromosome distribution to daughter cells Figure 8.4C Chromosome duplication and distribution. The term chromatid is used to describe duplicates that are connected at the centromere. This diagram emphasizes that the structures are called chromosomes when separated. This leads to a brief time when a cell has double the number of chromosomes, as in anaphase and telophase of mitosis, prior to cytokinesis. Chromosome duplication and distribution تضاعف وتوزيع الكروموزم Electron micrograph of a duplicated chromosome صورة بالمجهر لكروموزم متضاعف 8

The eukaryotic cell cycle دورة الخلية حقيقية النواة
8.5 The cell cycle multiplies cells تعمل دورة الخلية على مُضاعفة الخلايا The cell cycle is an ordered sequence of events for cell division دورة الخلية هي عملية تسلسلية مُنظمة للانقسام الخلوي It consists of two stages وتتكون من مرحلتين INTERPHASE Interphase: duplication of cell contents الطور البيني: مضاعفة محتويات الخلية G1: growth, increase in cytoplasm - نمو وزيادة السيتوبلازم. G1 S: duplication of chromosomes - مضاعفة الكروموزومات S G2: growth, preparation for division - التمهيد للإنقسام G2 Mitotic phase: division مرحلة الانقسام الفتيلي: الانقسام Mitosis: division of the nucleus الانقسام الفتيلي: انقسام النواة Cytokinesis: division of cytoplasm انقسام السيتوبلازم: الانقسام السيتوبلازمي S (DNA synthesis) G1 Cytokinesis G2 Mitosis Differences in the length of the cell cycle can be instructive. Yeast cells have a 2-hour life cycle, while human cells in culture take about 24 hours to divide. Mitosis and cytokinesis represent a shorter section of the cycle, lasting one hour for cultured human cells. Teaching Tips 1.The authors note in Module 8.5 that each of your students consists of about 100 trillion cells. It is likely that this number is beyond comprehension for most of your students. Consider sharing several simple examples of the enormity of that number to try to make it more meaningful. For example, the U.S. population in 2008 is about 310 million people. To give every one of those people about $323,000, we will need a total of $100 trillion. Here is another example. If we give you $31,688 every second of your life, and you lived for 100 years, you would receive $100 trillion dollars. 2.The concepts of DNA replication and sister chromatids are often obstacles for many students. If you can find twist ties or other bendable wire, you can demonstrate or have students model the difference between (1) a chromosome before DNA replication and (2) sister chromatids after DNA replication. One piece of wire will represent a chromosome before replication. Two twist ties twisted about each other can represent sister chromatids. We have doubled the DNA, but the molecules remain attached (although not attached in the same way as the wire). You might also want to point out that when sister chromatids are separated, they are considered separate chromosomes. 3. In G1, the chromosomes have not duplicated. But by G2, chromosomes consist of sister chromatids. If you have created a demonstration of sister chromatids, relate DNA replication and sister chromatids to the cell cycle. MITOTIC PHASE (M) The eukaryotic cell cycle دورة الخلية حقيقية النواة Copyright © 2009 Pearson Education, Inc. 9

Mitosis progresses through a series of stages
8.6 Cell division is a continuum of dynamic changes الانقسام الخلوي تغيرات حركية مستمرة Mitosis progresses through a series of stages يتم الانقسام الفتيلي عبر سلسلة من الأطوار المتتالية Prophase الطور التمهيدي Prometaphase الطور ما قبل الاستوائي Metaphase الطور الاستوائي Anaphase الطور الانفصالي Telophase الطور النهائي Cytokinesis often overlaps telophase الانقسام السيتوبلازمي غالباً ما يتداخل مع الطور النهائي Teaching Tips 1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym. 2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research. Copyright © 2009 Pearson Education, Inc. 10

8.6 Cell division is a continuum of dynamic changes الانقسام الخلوي تغيرات حركية مستمرة
A mitotic spindle is required to divide the chromosomes إن المغزل الفتيلي مطلوب لانقسام الكروموزمومات The mitotic spindle is composed of microtubules يتكون المغزل الفتيلي من أنبيبات دقيقة It is produced by centrosomes, structures in the cytoplasm that: تقوم الأجسام المركزية بإنتاجه, وهي التراكيب السيتوبلازمية المسئولة عن: Organize microtubule arrangement تنظيم وترتيب الأنبيبات الدقيقة Contain a pair of centrioles in animal cells تحتوي على زوجين من الجسيمات المركزية في كل خلية حيوانية The role of centrioles in cell division is unclear دور الجسيمات المركزية في الانقسام الخلوي غير معروف Centrioles give rise to basal bodies that are the foundations for cilia and flagella. They are found in animal cells but also in plants such as mosses and ferns that have swimming sperm. They are not found in flowering plants, showing that centrioles are not essential for spindle formation. There is other evidence, however, that suggests centrioles may influence progression through alternative stages in the cell cycle, including entry into the S phase and completion of cytokinesis. (Reviewed in A. W. Murray, 2001, “Centrioles at the Checkpoint,” Science, 291:1499–1501.) For the BioFlix Animation Mitosis, go to Animation and Video Files. Teaching Tips 1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym. 2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research. Copyright © 2009 Pearson Education, Inc. 11

INTERPHASE الطور البيني PROPHASE الطور التمهيدي
INTERPHASE الطور البيني PROPHASE الطور التمهيدي PROMETAPHASE طور ما قبل الاستوائي Centrosomes (with centriole pairs) Chromatin Early mitotic spindle مغزل فتيلي مبكر Centrosome جسم مركزي Fragments of Nuclear envelope شظايا الغلاف النووي Kinetochore مركز الحركة Figure 8.6 The stages of cell division. Nuclear Envelope الغلاف النووي Plasma Membrane الغشاء البلازمي Centromere القطعة المركزية Spindle Microtubules أنيبيات دقيقة مغزلية Nucleolus النوية Chromosome, consisting of two sister chromatids الكروموزم يتكون من كروماتيدتين شقيقة 12

Interphase الطور البيني
8.6 Cell division is a continuum of dynamic changes الانقسام الخلوي تغيرات حركية مستمرة Interphase الطور البيني In the cytoplasm في السيتوبلازم Cytoplasmic contents double تضاعُف المحتويات السيتوبلازمية Two centrosomes form تكوين اثنين من الاجسام المركزية In the nucleus في النواة Chromosomes duplicate during the S phase S تتضاعف الكروموزومات أثناء طور Nucleoli, sites of ribosome assembly, are visible تصبح النويات ”مواضع تصنيع الريبوسومات“ مرئية Teaching Tips 1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym. 2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research. Copyright © 2009 Pearson Education, Inc. 13

التخصر تكون الغلاف النووي
ANAPHASE الطور الانفصالي TELOPHASE AND CYTOKINESIS الطور النهائي والانقسام السيتوبلازمي METAPHASE الطور الاستوائي Metaphase plate الصفيحة الاستوائية Cleavage furrow التخصر Nucleolus Forming تكون النويه Figure 8.6 The stages of cell division. Nuclear envelope Forming تكون الغلاف النووي Spindle مغزل Daughter chromosomes كروموزومات شقيقة 14

8.7 Cytokinesis differs for plant and animal cells يختلف الانقسام السيتوبلازمي في النبات عن الحيوان
Cytokinesis الانقسام الخلوي Cleavage in animal cells التخصر في الخلايا الحيوانية A cleavage furrow forms from a contracting ring of microfilaments, interacting with myosin يتكون أخدود التخصر بواسطة حلقة منقبضة من الخيوط الدقيقة المتفاعلة مع الميوسين The cleavage furrow deepens to separate the contents into two cells يأخذ أخدود التخصر في التعمق فاصلاً بذلك المحتويات إلى خليتين Cytokinesis in plant cells الانقسام الخلوي في النبات A cell plate forms in the middle from vesicles containing cell wall material تتكون الصفيحة الخلوية في الوسط من حويصلات تحتوي على مادة الجدار الخلوي The cell plate grows outward to reach the edges, dividing the contents into two cells تنمو الصفيحة الخلوية بعيداً عن الوسط لتصل إلى الحواف, قاسمة بذلك المحتويات إلى خليتين Each cell has a plasma membrane and cell wall ولكل خلية غشاء بلازمي وجدار خلوي This material allows a review of cellular components. Students can be reminded that microtubules are composed of actin molecules and that actin and myosin work in concert for muscle cell contraction. They can also be reminded that vesicles have a lipid boundary that will contribute to the plasma membrane of the new plant cells. For the BLAST Animation Cytokinesis in Plants, go to Animation and Video Files. Teaching Tips 1. Many students think of mitosis and cytokinesis as one process. In some situations, mitosis occurs without subsequent cytokinesis. Challenge your students to predict the outcome of mitosis without cytokinesis (multinuclear cells called a syncytium). This occurs in human development during the formation of the placenta. 2. The authors make an analogy between a drawstring and the mechanism of cytokinesis in animal cells. Students seem to appreciate this association. Have your students think of a person tightening the drawstring of sweatpants so tight that they pinch themselves in two, or perhaps nearly so! The analogy is especially good because, like the drawstring just beneath the surface of the sweat pants, the microfilaments are just beneath the surface of the cell’s plasma membrane. Copyright © 2009 Pearson Education, Inc. 15

انقباض حلقي من الخيوط الدقيقة
Cleavage furrow أخدود التفلج Contracting ring of Microfilaments انقباض حلقي من الخيوط الدقيقة Figure 8.7A Cleavage of an animal cell. Daughter cells خليتين شقيقتين 16

الجدار الخلوي للخلية الأم
Wall of parent cell الجدار الخلوي للخلية الأم Cell plate forming تكون الصفيحة الخلوية Daughter nucleus النواة البنويه Cell wall جدار خلوي New cell wall جدار خلوي جديد Figure 8.7B Cell plate formation in a plant cell. Vesicles containing cell wall material حويصلات تحتوي على مادة الجدار الخلوي Cell plate صفيحة خلوية Daughter cells خليتان بنويتان 17

Growth (in an onion root)
Figure 8.11A Growth (in an onion root). Growth (in an onion root) النمو (في احدي جذور نبات البصل)

الطور الإنفصالى المبكر الطور الإنفصالى المتوسط الطور الإنفصالى المتأخر
Mitosis الإنقسام الميتوزى Metaphase الطور الإستوائى Early Anaphase الطور الإنفصالى المبكر Midi Anaphase الطور الإنفصالى المتوسط Late Anaphase الطور الإنفصالى المتأخر prophase الطور التمهيدى Telophase الطور النهائى

MEIOSIS AND CROSSING OVER الانقسام الاختزالي والعبور الوراثي
Copyright © 2009 Pearson Education, Inc. 20

8.12 Chromosomes are matched in homologous pairs تتوافق الكروموزومات في أزواج متماثلة
Somatic cells have pairs of homologous chromosomes, receiving one member of each pair from each parent الخلايا الجسدية لديها أزواج من الكروموزومات المتماثلة, والتي تستقبل عضو واحد من كل زوج من كل أبوين Homologous chromosomes are matched in تتوافق الكروموزومات المتماثلة في Length الطول Centromere position موقع القطعة المركزية Gene locations مواقع الجينات A locus (plural, loci) is the position of a gene الموضع هو المكان الذي يحتله الجين Different versions of a gene may be found at the same locus on maternal and paternal chromosomes يمكن أن تكون هناك عدة هيئات مختلفة للجين وهو في نفس موضعه سواءا على الكروموزومات الأم أو الأب Student Misconceptions and Concerns 1. Some students might conclude that sex chromosomes function only in determining the sex of the individual. As the authors note, sex chromosomes contain genes not involved in sex determination. Teaching Tips 1. Students might recall some basic genetics, remembering that for many traits a person receives a separate “signal” from mom and dad. These separate signals for the same trait are carried on the same portion of homologous chromosomes, such as the freckle trait discussed in Module 8.12. 2. Consider helping students through mitosis and meiosis by developing an analogy to pairs of shoes. In this case, any given species has a certain number of pairs of shoes, or homologous chromosomes. 3. In the shoe analogy, females have 23 pairs of matching shoes, while males have 22 matching pairs and 1 odd pair Maybe a sandal and a sneaker! Copyright © 2009 Pearson Education, Inc. 21

Homologous pair ofchromosomes A homologous pair of chromosomes
8.12 Chromosomes are matched in homologous pairs تتوافق الكروموزومات في أزواج متماثلة Homologous pair ofchromosomes زوج كروموزومي متماثل The human sex chromosomes X and Y differ in size and genetic composition تختلف الكروموزومات الجنسية البشرية X و Y في الحجم وفي التركيب الجيني Pairs of autosomes have the same size and genetic composition تمتلك أزواج الكروموزومات الذاتية نفس الحجم والتركيب الجيني Centromere القطعة المركزية Applying Your Knowledge Humans have 46 chromosomes; how many homologous pairs does that represent? 23 If there is one pair of sex chromosomes, how many pairs of autosomes are found in humans? 22 Student Misconceptions and Concerns 1. Some students might conclude that sex chromosomes function only in determining the sex of the individual. As the authors note, sex chromosomes contain genes not involved in sex determination. Teaching Tips 1. Students might recall some basic genetics, remembering that for many traits a person receives a separate “signal” from mom and dad. These separate signals for the same trait are carried on the same portion of homologous chromosomes, such as the freckle trait discussed in Module 8.12. 2. Consider helping students through mitosis and meiosis by developing an analogy to pairs of shoes. In this case, any given species has a certain number of pairs of shoes, or homologous chromosomes. 3. In the shoe analogy, females have 23 pairs of matching shoes, while males have 22 matching pairs and 1 odd pair Maybe a sandal and a sneaker! Sister chromatids الكروماتيدات الشقيقة One duplicated chromosome كروموزوم متضاعف A homologous pair of chromosomes زوج كروموزومي متماثل 22

8.13 Gametes have a single set of chromosomes الجاميطات بها مجموعة أحادية من الكروموزومات
Meiosis is a process that converts diploid nuclei to haploid nuclei الانقسام الاختزالي هي العملية التي تتحول بها النواة الثنائية إلى نواة أحادية Diploid cells have two homologous sets of chromosomes الخلايا الثنائية بها مجموعتين متماثلة من الكروموزومات ”العدد الكروموزومي الثنائي“ Haploid cells have one set of chromosomes الخلايا الأحادية بها مجموعة أحادية من الكروموزومات ”العدد الكروموزومي الأحادي“ Meiosis occurs in the sex organs, producing gametes—sperm and eggs يحدث الانقسام الاختزالي في الأعضاء التناسلية منتجاً الجاميطات وهي الحيوانات المنوية والبيض بكل منهما العدد الكروموزومي الأحادي Fertilization is the union of sperm and egg الاخصاب هو اتحاد الحيوان المنوي بالبيضة The zygote has a diploid chromosome number, one set from each parent يوجد باللاقحة ”الخلية المُخصبة“ العدد الكروموزومي الثنائي بمساهمة مجموعة كروموزومية من كل أب Teaching Tips 1. You might want to get your students thinking by asking them why eggs and sperm are different. (This depends upon the species, but within vertebrates, eggs, and sperm are specialized for different tasks. Sperm are adapted to move to an egg and donate a nucleus. Eggs contain a nucleus and most of the cytoplasm of the future zygote. Thus eggs are typically larger, nonmotile, and full of cellular resources to sustain cell division and growth.) 23

The human life cycle دورة حياة الانسان
Haploid gametes (n = 23) جاميطات أحادية العدد الكروموزومي n Egg cell خلية بيضية n Sperm cell خلية منوية Meiosis الانقسام الاختزالي Fertilization الإخصاب Diploid zygote (2n = 46) اللاقحة ثنائية العدد الكروموزومي 2n Multicultural diploid Adults (2n = 46) فردان بالغان يتكون كل منهما من خلايا ثنائية العدد الكروموزومي Figure 8.13 The human life cycle. Mitosis and development الانقسام الفتيلي والنمو الجنيني The human life cycle دورة حياة الانسان 24

Like mitosis, meiosis is preceded by interphase
8.14 Meiosis reduces the chromosome number from diploid to haploid الانقسام الاختزالي يعمل على تنصيف العدد الكروموزومي الثنائي إلى العدد الكروموزومي أحادي Like mitosis, meiosis is preceded by interphase يُفتتح الانقسام الاختزالي بالطور البيني مثله مثل الانقسام الفتيلي Chromosomes duplicate during the S phase تتضاعف الكروموزومات خلال مرحلة S Unlike mitosis, meiosis has two divisions الانقسام الاختزالي يتكون من انقسامين متتاليين بعكس الانقسام الفتيلي During meiosis I, homologous chromosomes separate يتم انفصال الأزواج الكروموزومية المتماثلة أثناء الانقسام الاختزالي الأول The chromosome number is reduced by half يتم اختزال عدد الكروموزومات إلى النصف During meiosis II, sister chromatids separate يتم انفصال الكروماتيدات الشقيقة أثناء الانقسام الاختزالي الثاني The chromosome number remains the same يبقي العدد الكروموزومي كما هو Student Misconceptions and Concerns 1. Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling is prevented if each gamete has only half the genetic material of the adult cells. 2. How meiosis results in four haploid cells, yet mitosis yields two diploid cells, is often memorized but seldom understood. It can be explained like this. Consider a pair of chromosomes in a cell before any cell divisions. This pair of chromosomes duplicates such that two chromosomes become four (although each pair of sister chromatids are joined at their centromeres). Therefore, mitosis and meiosis each typically begin with four chromosomes. Mitosis divides once, producing two cells, each with two chromosomes. Meiosis divides twice, sorting the four chromosomes into four separate cells. Teaching Tips 1. In meiosis I and meiosis II, the processes begin with duplicated pairs of chromosomes. This pair becomes two pairs. The two pairs include four items. Sort this group into two subgroups, and you are back to two pairs. Divide again, and you have separated four items into four groups of one. This can work with the shoe analogy if you wish to continue the reference. A pair of shoes is “reproduced” and becomes two pairs. Mitosis sorts them back into two pairs of shoes. However, meiosis keeps sorting, eventually isolating each shoe. Each solitary shoe would then represent a gamete, which would then be matched with another similar shoe (gamete) to make a new pair of shoes (organism). 25

Events in the nucleus during meiosis I Prophase I الطور التمهيدي الأول
8.14 Meiosis reduces the chromosome number from diploid to haploid الانقسام الاختزالي يعمل على تنصيف العدد الكروموزومي الثنائي إلى العدد الكروموزومي أحادي Events in the nucleus during meiosis I الأحداث التي تجري في النواة أثناء الانقسام الاختزالي الأول Prophase I الطور التمهيدي الأول Chromosomes coil and become compact تلتف الكروموزومات وتصبح مضغوطة Homologous chromosomes come together as pairs by synapsis تقترب الكروموزومات المتماثلة من بعضها البعض متزاوجة بعملية الاقتران Each pair, with four chromatids, is called a tetrad كل زوج كروموزومي به أربع كروماتيدات يسمي وحدة رباعية الكروموزوم Nonsister chromatids exchange genetic material by crossing over تتبادل الكروماتيدات غير الشقيقة المادة الوراثية بعملية العبور الوراثي Sister chromatids are exact duplicates, but nonsister chromatids belong to different members of the homologous pair. Any one of the maternal chromatids is a nonsister to any of the paternal chromatids. Since maternal and paternal chromatids can have different versions of genes (alleles) at corresponding loci, crossing over potentially produces new genetic combinations, mixing maternal and paternal versions on the same chromatid. Student Misconceptions and Concerns 1. Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling is prevented if each gamete has only half the genetic material of the adult cells. 2. How meiosis results in four haploid cells, yet mitosis yields two diploid cells, is often memorized but seldom understood. It can be explained like this. Consider a pair of chromosomes in a cell before any cell divisions. This pair of chromosomes duplicates such that two chromosomes become four (although each pair of sister chromatids are joined at their centromeres). Therefore, mitosis and meiosis each typically begin with four chromosomes. Mitosis divides once, producing two cells, each with two chromosomes. Meiosis divides twice, sorting the four chromosomes into four separate cells. Teaching Tips 1. In meiosis I and meiosis II, the processes begin with duplicated pairs of chromosomes. This pair becomes two pairs. The two pairs include four items. Sort this group into two subgroups, and you are back to two pairs. Divide again, and you have separated four items into four groups of one. This can work with the shoe analogy if you wish to continue the reference. A pair of shoes is “reproduced” and becomes two pairs. Mitosis sorts them back into two pairs of shoes. However, meiosis keeps sorting, eventually isolating each shoe. Each solitary shoe would then represent a gamete, which would then be matched with another similar shoe (gamete) to make a new pair of shoes (organism). 26

أطوار الانقسام الاختزالي الأول
MEIOSIS I: Homologous chromosomes separate الانقسام الاختزالي الأول: انفصال الأزواج الكروموزمومية المتماثلة INTERPHASE الطور البيني PROPHASE I الطور التمهيدي الأول METAPHASE I الطور الاستوائي الأول ANAPHASE I الطور الانفصالي الأول Centrosomes (with Centriole pairs) الأجسام المركزية (وبها أزواج الجسيمات المركزية) Sites of crossing over مواقع العبور الوراثي Microtubules attached to Kinetochore الأنبيبات الدقيقة متصلة بمركز الحركة Metaphase Plate الصفيحة الاستوائية Sister chromatids remain attached تبقي الكروماتيدات الشقيقة متصلة Spindle مغزل Figure 8.14 The stages of meiosis. Nuclear Envelope الغلاف النووي Sister Chromatids كروماتيدتين شقيقة Tetrad وحدة رباعي الكروموزوم Centromere (with kinetochore) القطعة المركزية (وبها مركزالحركة) Chromatin الكروماتين Homologous chromosomes separate انفصال الكرزموزومات المتماثلة The stages of miosis I أطوار الانقسام الاختزالي الأول 27

أطوار الانقسام الاختزالي الثاني
MEIOSIS II: Sister chromatids separate الانقسام الاختزالي الثاني: انفصال الكروماتيدات الشقيقة TELOPHASE I AND CYTOKINESIS الطور النهائي الأول والانقسام السيتوبلازمي PROPHASE II الطور التمهيدي الثاني METAPHASE II الطور الاستوائي الثاني ANAPHASE II الطور الانفصالي الثاني TELOPHASE II AND CYTOKINESIS الطور النهائي الثاني والانقسام السيتوبلازمي Cleavage furrow أخدود التخصر Sister chromatids Separate انفصال الكروماتيدات الشقيقة Haploid daughter cells forming تكون الخلايا الأحادية البنوية Figure 8.14 The stages of meiosis. The stages of miosis II أطوار الانقسام الاختزالي الثاني 28

الطور الإنفصالى الثانى
MEIOSIS الإنقسام الميوزى A B C D E F G H I PROPHASE I الطور التمهيدى الأول METAPHASE I الطور الإستوائى الأول ANAPHASE I الطور الإنفصالى الأول TELOPHASE I الطور النهائى الأول PROPHASE II الطور التمهيدى الثانى METAPHASE II الطور الإستوائى الثانى ANAPHASE II الطور الإنفصالى الثانى TELOPHASE II الطور النهائى الثانى TETRAD الطور رباعى الخلايا ANAPHASE II الطور الإنفصالى الثانى TELOPHASE II الطور النهائى الثانى TETRAD الطور رباعى الخلايا

Patterns of أنماط Inheritanceالوراثة
Chapter 9 الباب التاسع Patterns of أنماط Inheritanceالوراثة Lecture by Richard L. Myers Translated by Nabih A. Baeshen 30

9.1 The science of genetics has ancient roots إن علم الوراثة ذو جذور قديمة
Pangenesis was an early explanation for inheritance كانت نظرية شمولية التكوين إحدى التفسيرات المبكرة للوراثة It was proposed by Hippocrates اقترحها أبقراط Particles called pangenes came from all parts of the organism to be incorporated into eggs or sperm هناك جسيمات تسمي جينات شمولية تأتي من جميع أجزاء الكائن الحي لتستقر في البيض أو الحيوانات المنوية Characteristics acquired during the parents’ lifetime could be transferred to the offspring يمكن توريث الصفات التي يكتسبها الأبوين أثناء حياتهما للذرية Aristotle rejected pangenesis and argued that instead of particles, the potential to produce the traits was inherited رفض أرسطو نظرية شمولية التكوين واقترح أنه بدلاً من الجسيمات, فإن ما يورث هو الاستعداد لتوريث الصفات Blending was another idea, based on plant breeding الخلط كان فكرة أخرى, قائمة على التهجين النباتي Hereditary material from parents mixes together to form an intermediate trait, like mixing paint تختلط المادة الوراثية من الأبوين مُكونة صفات بينية, مثل خلط الألوان Ask students to give examples that contradict these early proposals. Most will agree that if something happens to a parent during his/her lifetime, the children do not inherit the change, as suggested by this real-life example: A man who lost part of his thumb in an accident became the father of five children, each with fully formed thumbs. Skin color may appear as a blended trait, since children of dark- and light-skinned parents are often intermediate between the two. However, two parents with intermediate skin color can have children with darker or lighter skin than either parent. (See Module 9.14.) In England, there was a recent report of two parents with medium skin color having twin daughters, one with light skin and the other with dark skin. Teaching Tips 1. As you begin your lectures on genetics, consider challenging your students to explain why the theories of pangenesis and blending are incorrect. Perhaps just pick one of the two. You might even ask for short responses from everyone at the start of class or as an assignment before the first lectures. In addition to arousing interest in the answers, the responses should reveal the diverse backgrounds of your students entering this discussion and reveal any preexisting confusion on the subject of genetics. 2. The concept of pangenesis is analogous to the structure of United States representation in Congress. Each congressional district sends a congressman or congresswoman (pangene) to the U.S. House of Representatives (gamete). There, all parts of the United States (body) are represented. 3. In this or future lectures addressing evolution, you may mention that pangenesis is a mechanism that permits Lamarckian evolution. Copyright © 2009 Pearson Education, Inc.

9.2 Experimental genetics began in an abbey garden بدأت التجارب الوراثية في حديقة دير (كنيسة)
Gregor Mendel discovered principles of genetics in experiments with the garden pea توصل جريجور مندل إلى مبادئ الوراثة بتجاربه التي أجراها على البسلة Mendel showed that parents pass heritable factors to offspring (heritable factors are now called genes) أوضح مندل أن الذرية ترث العوامل الوراثية من الأبوين (تسمي العوامل الوراثية حالياً الجينات) Advantages of using pea plants مزايا استخدام نبات البسلة Controlled matings التزاوج المضبوط ”الضابط“ Self-fertilization or cross-fertilization الاخصاب الذاتي أو الاخصاب الخلطي Observable characteristics with two distinct forms يوجد لكلٍ من الصفات الملحوظة هيئتين متميزتين True-breeding strains سلالات نقيه Student Misconceptions and Concerns 1. The authors note that Mendel’s work was published in 1866, seven years after Darwin published Origin of Species. Consider challenging your students to consider whether Mendel’s findings supported Darwin’s ideas. Some scientists have noted that Darwin often discussed the evolution of traits by matters of degree. Yet, Mendel’s selection of pea plant traits typically showed complete dominance, rather than the possibility for such gradual inheritance. Teaching Tips 1. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress. Copyright © 2009 Pearson Education, Inc.

Mendel’s technique for cross-fertilization of pea plants
Removed إزاحة stamens الأسدية From من Purple Flower الزهرة البنفسجية White ابيض 1 Stamens السداة Carpel الكربلة 2 Transferred pollen from stamens of White flower to carpel of purple flower نقل حبوب اللقاح من أسدية الزهرة البيضاء إلى كربلة الزهرة البنفسجية Parents (P) الآباء Purple بنفسج 3 Pollinated carpel matured into pod نضجت الكربلة الملقحة مكونة القرن الذي به البذور 4 Planted seeds from pod البذور المزروعة من القرن Figure 9.2C Mendel’s technique for cross-fertilization of pea plants. This slide demonstrates how Mendel could control matings between pea plants. He removed the pollen-bearing structures from one parental plant and transferred pollen from another parental plant. The true-breeding parental plants are called the P generation, their offspring are the F1 generation, and offspring of an F1  F1 cross are the F2 generation. Offspring (F1) الذرية Mendel’s technique for cross-fertilization of pea plants التقنية التي استخدمها مندل للقيام بالاخصاب الخلطي لنبات البسلة

The seven pea characteristics studied by Mendel
Character Dominant Trait Recessive Trait الهيئة المتنحية الهيئة السائدة الصفة Flower color لون الزهرة Purple بنفسجي White أبيض Terminal طرفي Flower position موضع الزهرة Axial جانبي Seed color لون البذرة Yellow أصفر Green أخضر Seed shape شكل البذرة Round مستدير Wrinkled مجعد Pod shape شكل قرن البذور Inflated كاملة Constricted مُخصره Pod color لون قرن البذور Yellow صفراء Figure 9.2D The seven pea characters studied by Mendel. Mendel studied seven characteristics for pea plants. Later studies have shown that pea plants have seven pairs of chromosomes, and each of these characteristics is on a different chromosome. This explains why Mendel’s results were not affected by genetic recombination. Green خضراء Stem length طول الساق Tall طويل Dwarf قصير The seven pea characteristics studied by Mendel الصفات السبعة التي درسها مندل 35

Example of a monohybrid cross مثال لتهجين أحادى
9.3 Mendel’s law of segregation describes the inheritance of a single character يصف قانون الافتراق لمندل كيفية وراثة صفة واحدة Example of a monohybrid cross مثال لتهجين أحادى Parental generation: purple flowers  white flowers الجيل الأبوي : الزهور البنفسجية × الزهور البيضاء F1 generation: all plants with purple flowers جيل الذرية 1الأول: كل النباتات لها زهور بنفسجية F2 generation: of plants with purple flowers of plants with white flowers جيل الذرية 2: نباتات لها زهور بنفسجية نباتات لها زهور بيضاء Mendel needed to explain استعان مندل لتفسير هذه النتائج ”بالإجابة على الأسئلة التالية“ Why one trait seemed to disappear in the F1 generation ما سبب اختفاء هيئة واحدة في جيل الذرية 1 Why that trait reappeared in one quarter of the F2 offspring ما سبب عودة ظهور تلك الهيئة في ربع من الذرية 2 For the BLAST Animation Single-Trait Crosses, go to Animation and Video Files. Student Misconceptions and Concerns 1. Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. Just as we would expect that any six playing cards dealt might be half black and half red, we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios. Teaching Tips 1. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress. 2. Many students benefit from a little quick practice with a Punnett square. Have them try these crosses for practice: (a) PP pp and (b) Pp pp. 3. For students struggling with basic terminology, an analogy between a genetic trait and a pair of shoes might be helpful. A person might wear a pair of shoes in which both shoes match (homozygous), or less likely, a person might wear shoes that do not match (heterozygous). 4. Another analogy that might help struggling students is a pair of people trying to make a decision about where to eat tonight. One person wants to eat at a restaurant, the other wants to eat a meal at home. This (heterozygous) couple eats at home (the dominant allele “wins”). 5. Figure 9.4 can be of great benefit when introducing genetic terminology of genes. For students struggling to think abstractly, such a visual aid may be essential when describing these features in lecture. Copyright © 2009 Pearson Education, Inc. 36

P generationجيل أبوى (true-breeding (نسل parents) أبوي نقي)
Purple flowers زهور بنفسجية White flowers زهور بيضاء All plants have purple flowers كل النباتات لها زهور بنفسجية F1 generation جيل الذرية 1 Fertilization among F1 plants (F1 ´ F1) الاخصاب بين نباتات الذرية 1 (الذرية 1 مع الذرية 1) Figure 9.3A Crosses tracking one character (flower color). F2 generation جيل الذرية 2 ¾ of plants have purple flowers ¾ النباتات لها زهور بنفسجية ¼ of plants have white flowers ¼ النباتات لها زهور بيضاء Crosses tracking one character (flower color) متابعة وراثة صفة واحدة من خلال التهجينات المتتالية (لون الزهرة) 37

Explanation of the crosses in previous figure
Genetic makeup (alleles) النوع الجيني (الأليلات) P plants نباتات الجيل الأبوي PP pp P p P Gametesالجاميطات p All P All p P F1 plants (hybrids) نباتات الجيل 1 (هجن) All Pp p P p Gametesالجاميطات 1 – 2 P 1 – 2 p P Sperm اللقاح p Figure 9.3B Explanation of the crosses in Figure 9.3A. A Punnett square is used to show all possible fertilization events for parental gametes. In three quarters of the F2 genotypes, there will be at least one dominant allele. P p Phenotypic ratio 3 purple : 1 white النسبة المظهرية 3 بنفسجي: 1 أبيض P F2 plants نباتات الجيل 2 P PP Pp Eggs البيض Genotypic ratio 1 PP : 2 Pp : 1 pp النسبة الوراثية p p Pp pp Explanation of the crosses in previous figure تفسير التهجينات ”التلقيحات“ في الشكل السابق

P a P a PP aa Genotype: النوع الوراثي
Gene loci مواقع الجينات Dominant allele أليل سائد P a B P a b Recessive allele أليل متنحي Figure 9.4 Matching gene loci on homologous chromosomes. Genotype: النوع الوراثي PP aa Bb Homozygous نقي for the للأليل السائد dominant allele Homozygous نقي for theللأليل المتنحي recessive allele Heterozygous خليط Matching gene loci on homologous chromosomes توافق مواقع الجينات على الكروموزومات المتماثلة 39

9.8 CONNECTION: Genetic traits in humans can be tracked through family pedigrees رابطة تطبيقية: يمكن اقتفاء أثر الهيئات الوراثية في الانسان عبر شجرة نسب الأسرة A pedigree شجرة النسب Shows the inheritance of a trait in a family through multiple generations توضح توارث الهيئة في أسرة ما عبر أجيال متتالية Demonstrates dominant or recessive inheritance تبين الهيئة الوراثية السائدة أو المتنحية Can also be used to deduce genotypes of family members يمكن استخدامها أيضاً لاستنتاج الأنواع الوراثية لأعضاء الأسرة Student Misconceptions and Concerns 1. Students might think that dominant alleles are naturally (a) more common, (b) more likely to be inherited, and (c) better for an organism. The text notes that this is not necessarily true. However, this might need to be emphasized further in the lecture. Teaching Tips 1. Students also seem to learn much from Figure 9.8b by analyzing the possible genotypes for the people whose complete genotype is not known. Consider challenging your students to suggest the possible genotypes for these people. Copyright © 2009 Pearson Education, Inc.

Examples of single-gene inherited traits in humans
الهيئات السائدة Dominant Traits Recessive Traits الهيئات المتنحية Freckles نمش No freckles بدون نمش Examples of single-gene inherited traits in humans أمثلة على طرق توريث بعض الهيئات في الانسان Figure 9.8A Examples of single-gene inherited traits in humans. This figure shows three traits that are determined by single genes with alternate alleles. The role of the dominant allele in influencing the phenotype when at least one copy is present can be emphasized here. Widow’s peak مقدمة الشعر البارزة Straight hairline مقدمة الشعر المستقيمة Free earlobe شحمة أذن حرة Attached earlobe شحمة أذن ملتحمة

Examples of single-gene inherited traits in humans
Examples of single-gene inherited traits in humans أمثلة على طرق توريث بعض الهيئات في الانسان Dominant Traits الهيئات السائدة Recessive Traits الهيئات المتنحية FF or Ff ff Genotype التركيب الجينى Figure 9.8A Examples of single-gene inherited traits in humans. Phenotype الشكل الظاهرى Free earlobe شحمة أذن حرة Attached earlobe شحمة أذن ملتحمة

Ff Ff ff Ff FF ff ff Ff Ff ff or Ff ff FF or Ff
First generation (grandparents) الجيل الأول (الأجداد) Ff Ff ff Ff Second generation (parents, aunts, and uncles) الجيل الثاني (الوالدين, الخالات والعمات, الأخوال والأعمام) FF ff ff Ff Ff ff or Ff Third generation (two sisters) الجيل الثالث (شقيقتان) ff FF or Female أنثي Male ذكر Figure 9.8B Pedigree showing inheritance of attached versus free earlobe in a hypothetical family. Ff Affectedمتأثرين ”ملتحمة“ Unaffectedغير متأثرين ”حرة“ Pedigree showing inheritance of attached versus free earlobe in a hypothetical family شجرة نسب توضح توريث شحمة أذن حرة مقابل أخرى ملتحمة في أسرة افتراضية

Parents الأبوين Normal Dd طبيعي Normal Dd طبيعي ´ D d Dd DD D Eggs بيض
Parents الأبوين Normal Dd طبيعي Normal Dd طبيعي Sperm الحيوانات المنوية D d Dd Normal (carrier) طبيعي“حامل“ DD Normal طبيعي D Eggs بيض Offspring الذرية Figure 9.9A Offspring produced by parents who are both carriers for a recessive disorder. This diagram shows the inheritance of deafness, a recessive trait, from two heterozygous parents. Dd Normal (carrier) طبيعي“حامل“ dd Deaf أَصَم d Offspring produced by parents who are both carriers for a recessive diorder ذرية والدين يحمل كلً منهما اضطراب متنحي

Table 9.9 Some Autosomal Disorders in Humans.

يتم علاجه بالتخلص من الجلاكتوز من النظام الغذائي
بعض اضطرابات الكرموزومات الجسدية في الانسان جدول 9.9 تعليقات نسبة الحدوث الأعراض الرئيسية الاضطراب الاضطرابات المتنحية مقدمة لسرطان الجلد 1/22.000 قلة الصبغة في الجلد, الشعر والعيون المهق راجع نموذج 9.9 1/ قوقازيين زيادة المخاط في الرئة, القناة الهضمية, الكب; زيادة القابلية للإصابة بالعدوى, الموت في سن مبكر من الطفولة إلا في حالة المعالجة التليف الحويصلي يتم علاجه بالتخلص من الجلاكتوز من النظام الغذائي 1/ تراكم الجلاكتوز في الأنسجة, الإعاقة العقلية, تلف العين والكبد تراكم الجلاكتوز راجع نموذج 9.10 1/ في أمريكا وأوروبا تراكم الفينل ألانين في الدم, نقص صبغة الجلد الطبيعية, الإعاقة العقلية إسوداد البول راجع نموذج 9.13 1/400 الأمريكان الأفارقة خلايا دم حمراء منجلية, تلف العديد من الأنسجة مرض الخلية المنجلية راجع نموذج 4.11 1/ 3500 يهود أوروبا الوسطي تراكم الدهون في خلايا المخ, القصور العقلي, العمي, الموت في الطفولة مرض تاي-ساش الاضطرابات السائدة 1/ التقزم نقص التعظم الغضروفي غير معروف تدهور القدرات العقلية, تحدث في أواخر العمر مرض الزهيمر ”نوع واحد“ 1/25.000وهم خليط تدهور القدرات العقلية وعدم القدرة على التحكم في الحركة, تحدث في منتصف العمر مرض هانتنجتون راجع نموذج 911 1/500 وهم خليط زيادة الكوليسرول في الدم, الأمراض القلبية ارتفاع الكوليسترول

VARIATIONS ON MENDEL’S LAWS الاختلافات عن قوانين مندل

Incomplete dominance السيادة غير التامة
9.11 Incomplete dominance results in intermediate phenotypes تؤدي السيادة غير التامة إلى أنواع وراثية وسطية Incomplete dominance السيادة غير التامة Neither allele is dominant over the other لا يسود أي أليل على الأخر Expression of both alleles is observed as an intermediate phenotype in the heterozygous individual يتم ملاحظة كلا الأليلين كنوع وراثي وسطي في الفرد الخليط Student Misconceptions and Concerns 1. After reading the preceding modules, students might expect all traits to be governed by a single gene with two alleles, one dominant over the other. Modules 9.11–9.15 describe deviations from this simplistic model of inheritance. 2. As these variations of Mendel’s laws are introduced, students are likely to get confused and become uncertain about the prior definitions. Consider keeping a clear definition of these different patterns of inheritance available for the class to refer to as new patterns are discussed (perhaps as a handout for student reference). 3. As your class size increases, the chances increase that at least one student will have a family member with one of the genetic disorders discussed. Some students may find this embarrassing, but others might have a special interest in learning more about these topics, and may even be willing to share some of their family’s experiences with the class. Teaching Tips 1. Incomplete dominance is analogous to a compromise, or a gray shade. The key concept is that both “sides” have input. Complete dominance is more analogous to an authoritarian style, overruling others and insisting on things being a certain way. Although these analogies might seem obvious to instructors, many students new to genetics appreciate them. 2. Another analogy for cholesterol receptors is fishing poles. The more fishing poles you use, the more fish you can catch. Heterozygotes for hypercholesterolemia have fewer “fishing poles” for cholesterol. Thus, fewer “fish” are caught and more “fish” remain in the water. Copyright © 2009 Pearson Education, Inc. 48

Incomplete dominance in snapdragon color
P generation الجيل الأبوي Red أحمر RR White أبيض rr Gametes الجاميطات R r F1 generation جيل الذرية 1 Pink قرمزي ”وردي“ Rr Gametes الجاميطات 1 – 2 R 1 – 2 r Sperm اللقاح Figure 9.11A Incomplete dominance in snapdragon color. This figure shows incomplete dominance in flower color. The difference in color between the RR and Rr genotypes is proposed to be a dosage effect, where the presence of one allele allows the production of half as much pigment as the presence of two alleles. R r 1 – 2 1 – 2 F2 generation جيل الذرية 2 1 – 2 R RR rR RR Eggs بيض r Rr rr 1 – 2 Incomplete dominance in snapdragon color السيادة غير التامة في لون زهور حنك السبع 49

When Mendel’s laws/results may not be observed
Extensions to Mendel When Mendel’s laws/results may not be observed Genetic Occurrence Definition Examples Polygenic inheritance وراثة التعدد الجينى More than one gene can affect a single trait أكثر من جين واحد يؤثر فى صفة مفردة 4 genes are involved in determining eye color. (لون العين) Human height (طول الإنسان) Pleiotropy الأثر المتعدد للجين A single gene can affect more than one trait جين مفرد يؤثر فى أكثر من صفة A pleiotropic allele dominant for yellow fur in mice is recessive for lethal developmental defect. (لون فراء الفئران الأصفر) Sickle cell anemia (أنيميا الخلايا المنجلية) Multiple alleles for one gene تعدد أليلى لجين واحد Genes may have more than two alleles جينات تملك أكثر من أليلين ABO blood types in humans (أنماط الدم ABO فى الإنسان) Dominance is not always complete السيادة ليست دائما كاملة In incomplete dominance the heterozygote is intermediate. In co-dominance no single allele is dominant, and the heterozygote shows some aspect of both homozygotes. Human blood groups (مجاميع دم الإنسان) Environmental factors عوامل بيئية Genes may be affected by the environment. Siamese cats (القطط السيامى) Gene interaction التفاعل الجينى Products of genes can interact to alter genetic ratios. منتجات الجينات تتفاعل لتغير من النسب الوراثية The production of a purple pigment in corn (إنتاج الصبغة الإرجوانى فى الذرة)

9.20 Chromosomes determine sex in many species تحدد الكروموزومات الجنس في العديد من الأنواع
X-Y system in mammals, fruit flies نظام X-Y مُتبع في الثدييات وذباب الفاكهة XX = female; XY = male XX = أنثي ; XY = ذكر X-O system in grasshoppers and roaches نظام X-O مُتبع في الجراد والصراصير XX = female; XO = male XX = أنثي ; XO = ذكر Z-W in system in birds, butterflies, and some fishes نظام Z-W في الطيور, الفراشات, وبعض الأسماك ZW = female, ZZ = male ZW= أنثي ; ZZ = ذكر Chromosome number in ants and bees نظام العدد الكروموزومي مُتبع في النمل والنحل Diploid = female; haploid = male العدد الكروموزومي للأنثي , العدد الكروموزومي للذكر While fruit flies have X and Y chromosomes, sex determination is influenced by the X chromosome to autosome ratio. Females with XX genotype have two X chromosomes and two sets of autosomes for an X:A ratio of 1. Males with XY genotype have one X chromosome and two sets of autosomes for an X:A ratio of 0.5. Teaching Tips 1. In certain animals, such as crocodilians and many turtles, sex is not genetically determined. Instead, the incubation temperature of the eggs determines an animal’s sex. Students may enjoy researching this unique form of sex determination, often identified as TSD (temperature-dependent sex determination). 51

الخلايا الأبوية ثنائية
(male) (ذكر) Sperm حيوانات منوية (female) (أنثي) 44 + XY Parents’ diploid cells الخلايا الأبوية ثنائية العدد الكروموزومي XX 22 X Y Egg بيضة Offspring (diploid) الذرية (ثنائية العدد الكروموزومي) X-Y system نظام X-Y Figure 9.20B The X-Y system. 52

CONNECTION: Male not female (responsible) for begetting either male or female babies رابطة تطبيقية: الذكر و ليس الانثى (مسئول) عن إنجاب مولود ذكراً كان أم أنثى يقول  تبارك و تعالى فى كتابه الحكيم فى (سورة القيامة): بسم الله الرحمن الرحيم أَيَحْسَبُ الْإِنسَانُ أَن يُتْرَكَ سُدًى 36 أَلَمْ يَكُ نُطْفَةً مِّن مَّنِيٍّ يُمْنَى 37  ثُمَّ كَانَ عَلَقَةً فَخَلَقَ فَسَوَّى 38 فَجَعَلَ مِنْهُ الزَّوْجَيْنِ الذَّكَرَ وَالْأُنثَى  39 صدق الله العظيم كانت إمرأة أبى حمزة الضبى شاعرة ، و قد هجرها زوجها حين ولدت بنتاً يوماً بخبائها ، فإذا هى تفول: ما لأبى حمزة لا يأتينا يظل فى البيت الذى يــلينا غضبـان ألا نلد الــبنينا تا الله ما ذلك فى ايـــــدينا و إنما نأخذ ما أعطــينا و نحن كالأرض لزارعينا تنبت ما قد زرعوه فينا فرق لها و صالحها

Chromosome number system نظام العدد الكروموزومي
22 + X XX X-O system نظام X-O 76 ZZ ZW Z-W system نظام Z-W 16 Chromosome number system نظام العدد الكروموزومي 32 Figure 9.20C The X-O system. 54

Molecular Biology of the Gene البيولوجيا الجزيئية للجين
Chapter 10 الباب العاشر Molecular Biology of the Gene البيولوجيا الجزيئية للجين Lecture by Richard L. Myers Translated by Nabih A. Baeshen

التركيب الجزيئي للمادة الوراثية
MOLECULAR STRUCTURE OF THE GENETIC MATERIAL التركيب الجزيئي للمادة الوراثية Copyright © 2009 Pearson Education, Inc.

10.2 DNA and RNA are polymers of nucleotides الدنا والرنا عبارة عن بوليمرات نيوكليوتيدية
The monomer unit of DNA and RNA is the nucleotide, containing وحدة التبلمر في الدنا والرنا تسمي نيوكليوتيدة, التي تحتوي على 5-carbon sugar سكر خُماسي الكربون Phosphate group مجموعة فوسفات Nitrogenous base قاعدة نيتروجينية A sugar-phosphate backbone is formed by covalent bonding between the phosphate of one nucleotide and the sugar of the next nucleotide يتكون عمود السكر والفوسفات بالارتباط التساهمي بين فوسفات إحدى النيوكليوتيدات وسكر النيوكليوتيدة التالية Nitrogenous bases extend from the sugar-phosphate backbone تبرز القواعد النيتروجينية من عمود السكر والفوسفات Student Misconceptions and Concerns 1. If your class has not yet studied Chapter 3, consider assigning module 3.16 on “Nucleic Acids” before addressing the contents of Chapter 10. 2. Students often confuse the terms nucleic acids, nucleotides, and bases. It helps to note the hierarchy of relationships: nucleic acids consist of long chains of nucleotides (polynucleotides), while nucleotides include nitrogenous bases. Teaching Tips 1. The descriptions of the discovery of DNA’s structure are a good time to point out that science is a collaborative effort. Watson, Crick, and Wilkins earned Nobel prizes due to their historic conclusions based upon the work of many others (including Griffith, Hershey, Chase, Franklin, and Chargaff). 2. Consider comparing DNA, RNA, and proteins to a train (polymer). DNA and RNA are like a train of various lengths and combinations of four types of train cars (monomers). Proteins are also “trains” of various lengths but made of a combination of 20 types of train cars. Copyright © 2009 Pearson Education, Inc.

The structure of DNA polynucleotide تركيب متعدد نيوكليوتيدات الدنا
Sugar-phosphate backbone عمود السكر والفوسفات Phosphate group مجموعة فوسفات Nitrogenous base قاعدة نيتروجينية Sugar سكر Nitrogenous base (A, G, C, or T) قاعدة نيتروجينية DNA nucleotide نيوكليوتيدة الدنا Phosphate group مجموعة فوسفات Thymine (T) الثايمين (T) Figure 10.2A The structure of a DNA polynucleotide. This figure shows a short stretch of DNA. The nucleotides can theoretically be arranged in any order, since all nucleotides have a phosphate group that can be joined to the sugar of any other nucleotide. The order of nucleotides within a gene, however, is what provides the information for producing a specific protein. Sugar (deoxyribose) السكر (الدي أوكسي رايبوز) DNA nucleotide نيوكليوتيدة الدنا DNA polynucleotide متعدد نيوكليوتيدات الدنا The structure of DNA polynucleotide تركيب متعدد نيوكليوتيدات الدنا

10.3 DNA is a double-stranded helix الدنا عبارة عن حلزون مزدوج الخيوط
DNA is composed of two polynucleotide chains joined together by hydrogen bonding between bases, twisted into a helical shape يتكون الدنا من سلسلتين من متعدد النيوكليوتيدات تتصل ببعضها البعض بروابط هيدروجينية بين القواعد النيتروجينية ملتفة حول بعضها البعض في شكل حلزوني The sugar-phosphate backbone is on the outside يوجد عمود السكر والفوسفات خارج الحلزون The nitrogenous bases are perpendicular to the backbone in the interior أما القواعد النيتروجينية فهي متعامدة على هذا العمود في داخلة Specific pairs of bases give the helix a uniform shape تتزاوج القاعدة النيتروجينية بطريقة خاصة معطية الحلزون شكل منتظم A pairs with T, forming two hydrogen bonds يتزاوج الأدنين من الثايمين فيكونا رابطتين هيدروجينية G pairs with C, forming three hydrogen bonds يتزاوج الجوانين مع السايتوسين فيكونا ثلاث روابط هيدروجينية The specific nature of the base-pairing interactions not only accounted for the uniform diameter of the double helix but also conformed to the chemical characteristics of the nucleotide bases and chemical composition studies of DNA. RNA molecules have secondary structure that involves hydrogen bonding between bases on the same polynucleotide chain. Thus the structure will be unique to RNA of a specific sequence. The covalent bonding between nucleotides can be contrasted with the hydrogen bonding between bases. Although individual hydrogen bonds are weaker than covalent bonds, the large number of hydrogen bonds along a double helical DNA molecule stabilizes the helix. Hydrogen bonds can be temporarily disrupted so that the DNA strands separate, but each individual strand remains intact. Student Misconceptions and Concerns 1. If your class has not yet studied Chapter 3, consider assigning module 3.16 on “Nucleic Acids” before addressing the contents of Chapter 10. 2. Students often confuse the terms nucleic acids, nucleotides, and bases. It helps to note the hierarchy of relationships: nucleic acids consist of long chains of nucleotides (polynucleotides), while nucleotides include nitrogenous bases. Teaching Tips 1. The descriptions of the discovery of DNA’s structure are a good time to point out that science is a collaborative effort. Watson, Crick, and Wilkins earned Nobel prizes due to their historic conclusions based upon the work of many others (including Griffith, Hershey, Chase, Franklin, and Chargaff). 2. The authors note that the structure of DNA is analogous to a twisted rope ladder. In class, challenge your students to explain what the parts of the ladder represent. The wooden rungs represent pairs of nitrogenous bases joined together by hydrogen bonds. Each rope represents a sugar-phosphate backbone. Copyright © 2009 Pearson Education, Inc.

Three presentations of DNA ثلاثة عروض لشكل الدنا
Hydrogen bond رابطة هيدروجين Base pair زوج قاعدي Figure 10.3D Three representations of DNA. Hydrogen bonding between bases can be seen in the partial chemical structure in the center. This figure can also be used to point out the opposite polarity of the DNA chains as emphasized in Module From top to bottom, the chain on the left is oriented 5  3 while the chain on the right is oriented 3  5. A 5 end has a free phosphate group attached to the 5 carbon of the sugar and a 3 end has a free –OH group attached to the 3 carbon of the sugar. Ribbon model النموذج الشريطي Partial chemical structure التركيب الكيميائي لجزء من الدنا Computer model نموذج حاسوبي Three presentations of DNA ثلاثة عروض لشكل الدنا

يمكن لتعبئة الدنا ان تمنع عملية النسخ
11.3 DNA packing in eukaryotic chromosomes helps regulate gene expression تعبئة الدنا في كروموزومات الكائنات حقيقية النواة تساعد في التحكم في التعبير الجيني Eukaryotic chromosomes undergo multiple levels of folding and coiling, called DNA packing تمر كروموزومات الكائنات حقيقية النواة بعدة مستويات من الطي والالتفاف, والتي تسمي تعبئة الدنا Nucleosomes are formed when DNA is wrapped around histone proteins تتكون الأجسام النووية عند التفاف الدنا حول البروتينات الهيستونيه “Beads on a string” appearance مظهر ”المَسبحة“ Each bead includes DNA plus 8 histone molecules تشمل كل حبة الدنا بالإضافة إلى 8 جزيئات هسيونية String is the linker DNA that connects nucleosomes الخيط هو الدنا الرابط الذي يصل ما بين الأجسام النووية Tight helical fiber is a coiling of the nucleosome string خيط الأجسام النووية عبارة عن ليفة مُحكمة الحلزنة Supercoil is a coiling of the tight helical fiber الحلزنة الفائقة هي التفاف الليفة محكمة الحلزنة Metaphase chromosome represents the highest level of packing يمثل كروموزم الطور الاستوائي أعلي مستوي من مستويات التعبئة (أقصي حالات الالتفاف والحلزنة والتكثف) DNA packing can prevent transcription يمكن لتعبئة الدنا ان تمنع عملية النسخ Student Misconceptions and Concerns 1. The broad concept of selective reading of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of software manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.9 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Just as boxes of things that you rarely use are packed into a closet, attic, or basement, chromatin that is not expressed is highly compacted, and stored deeply packed away. 2. Just as a folded map is difficult to read, DNA packaging tends to prevent gene reading or expression. Copyright © 2009 Pearson Education, Inc.

كروموزوم الطور الاستوائي
11.3 DNA packing in eukaryotic chromosomes helps regulate gene expression تعبئة الدنا في كروموزومات الكائنات حقيقية النواة تساعد في التحكم في التعبير الجيني DNA double helix (2-nm diameter) الحلزون المزدوج للدنا (القطر 2nm) “Beads on a string” مَسبحة Linker الدنا الرابط Histones الهيستونات Metaphase Chromosome كروموزوم الطور الاستوائي Tight helical fiber (30-nm diameter) ليفة مُحكمة الحلزوني (قطر 30 nm) Nucleosome (10-nm diameter) الجسم النووي (القطر 10nm) Supercoil (300-nm diameter) الحلزنة الفائقة (القطر 300nm) 700 nm Figure 11.3 DNA packing in a eukaryotic chromosome. This figure shows the increasing levels of DNA packing. The initial level of the nucleosome involves ~140 base pairs of DNA surrounding 8 molecules of histone proteins. A linker region of 40–60 nucleotides is found between nucleosomes. Histones are highly evolutionarily conserved proteins, with only two amino acid changes between histone H4 molecules in pea plants and cows. The combination of histones with DNA has long been associated with the inhibition of transcription. Histones have sites for acetylation in their amino-terminal regions that can reduce binding between positively charged lysine residues and negatively charged DNA. Histone acetylation has been correlated with increased transcriptional activity as it would allow for transient removal of the histone-protein portion of the nucleosome during transcription. DNA packing in a eukaryotic chromosome تعبئة الدنا في كروموزوم الكائنات حقيقية النواة

10.4 DNA replication depends on specific base pairing يتوقف تضاعف الدنا على خصوصية الارتباط بين القواعد النيتروجينية DNA replication follows a semiconservative model يتبع تضاعف الدنا نموذج شبة تحفظي The two DNA strands separate ينفصل خيطا الدنا Each strand is used as a pattern to produce a complementary strand, using specific base pairing ويستخدم كل خيط كقالب لإنتاج خيط مُكمل له, باستخدام خاصية الارتباط بين القواعد النيتروجينية Each new DNA helix has one old strand with one new strand كل حلزون دنا جديد به خيط قديم وخيط جديد Student Misconceptions and Concerns 1. The authors note that although the general process of semiconservative DNA replication is relatively simple, it involves complex biochemical gymnastics. The DNA molecule is unwound, each strand is copied simultaneously, the correct bases are inserted, and the product is proofread and corrected. Before discussing these details, be sure that your students understand the overall process, what is accomplished, and why each step is important. Teaching Tips 1. Demonstrate the complementary base pairing within DNA. Present students with the base sequence to one side of a DNA molecule and have them work quickly at their seats to determine the sequence of the complimentary strand. For some students, these sorts of quick practice are necessary to reinforce a concept and break up a lecture. 2. The authors note that the semiconservative model of DNA replication is like making a photo from a negative and then a new negative from the photo. In each new negative and photo pair, the new item was made from an old item. Copyright © 2009 Pearson Education, Inc.

A template mode for DNA replication النموذج القالبي لتضاعف الدنا
Untwisting and replication of DNA semiconservatively فك حلزنه الدنا وتضاعفه بالطريقة شبة التحفظية Figure 10.4A A template model for DNA replication. This figure emphasizes the accuracy of DNA replication, due to the specific base-pairing interactions. When the strand on the left is a template, the complementary strand is identical to the one on the right and vice versa. Nucleotides نيوكليوتيدات Parental molecule of DNA جزئ الدنا الأبوي Both parental strands serve as templates يستخدم كلاً من الخيطيين الأبوية كقالبين Two identical daughter molecules of DNA جزيئين بنوويين متماثلين للدنا A template mode for DNA replication النموذج القالبي لتضاعف الدنا

THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN
تدفق المعلومات الوراثية من الدنا إلى الرنا فالبروتين Copyright © 2009 Pearson Education, Inc.

الجين عبارة عن تسلسل من الدنا يوجه بناء نوع معين من البروتين
10.6 The DNA genotype is expressed as proteins, which provide the molecular basis for phenotypic traits النوع الوراثي للدنا يُعبر عنه بالبروتينات, التي توفر الأساس الجزئي للنوع المظهري للهيئات A gene is a sequence of DNA that directs the synthesis of a specific protein الجين عبارة عن تسلسل من الدنا يوجه بناء نوع معين من البروتين DNA is transcribed into RNA يتم استنساخ الدنا إلى الرنا RNA is translated into protein يتم ترجمة الرنا إلى البروتين The presence and action of proteins determine the phenotype of an organism توفر البروتينات وممارستها لوظائفها من شأنه تحديد النوع المظهري للكائن The role of proteins in expression of a genotype can be connected to the experiments that established the foundations of genetics. The round-wrinkled phenotypes of Mendel’s pea plants were due to differences in the production of a Starch Branching Enzyme (SBEI). The round-seeded plants had a functional version of the SBEI enzyme, allowing the formation of amylopectin, a highly branched form of starch, from sucrose. The wrinkled-seeded plants stored excess sucrose due to their lack of a functional SBEI enzyme and accumulated excess water as a result. When both types of seeds completed a natural dehydration process in seed maturation, the round seeds retained their shape, while the wrinkled seeds shriveled from water loss. Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. 2. Consider placing the basic content from Figure 10.6 on the board, noting the sequence, products, and locations of transcription and translation in eukaryotic cells. This reminder can create a quick concept check for students as they learn additional detail. Teaching Tips 1. It has been said that everything about an organism is an interaction between the genome and the environment. You might wish to challenge your students to explain the validity of this statement. 2. The information in DNA is used to direct the production of RNA, which in turn directs the production of proteins. However, in Chapter 3, four different types of biological molecules were noted as significant components of life. Students who think this through might wonder, and you could point out, that DNA does not directly control the production of carbohydrates and lipids. So how does DNA exert its influence over the synthesis of these two chemical groups? The answer is largely by way of enzymes, proteins with the ability to promote the production of carbohydrates and lipids. Copyright © 2009 Pearson Education, Inc.

Genotype النوع الوراثي Phenotype النوع المظهري
DNA الدنا Genotype النوع الوراثي Transcription النسخ RNA الرنا Nucleus النواة Cytoplasm السيتوبلازم Translation الترجمة Figure 10.6A Flow of genetic information in a eukaryotic cell. Transcription is the production of RNA using DNA as a template. In eukaryotic cells, transcription occurs in the nucleus, and the resulting RNA (mRNA) enters the cytoplasm. Translation is the production of protein, using the sequence of nucleotides in RNA. Translation occurs in the cytoplasm for both prokaryotic and eukaryotic cells. Phenotype النوع المظهري Protein بروتين Flow of genetic information in a eukaryotic cell تدفق المعلومات الوراثية في خلية حقيقية النواة

10.7 Genetic information written in codons is translated into amino acid sequences يتم ترجمة المعلومات الوارثية المكتوبة على هيئة شفرات إلى تسلسلات من الأحماض الامينية The sequence of nucleotides in DNA provides a code for constructing a protein يوفر تسلسل النيوكليوتيدات في الدنا الشفرات الوراثية اللازمة لبناء البروتين Protein construction requires a conversion of a nucleotide sequence to an amino acid sequence يتطلب بناء البروتين قلب تسلسل النيوكليوتيدات إلى تسلسل الأحماض الأمينية Transcription rewrites the DNA code into RNA, using the same nucleotide “language” تعيد عملية النسخ كتابة شفرة الدنا إلى الرنا, باستخدام نفس ”لغة ”النيوكليوتيدات Each “word” is a codon, consisting of three nucleotides كل ”كلمة“ عبارة عن شفرة, تتكون من ثلاث نيوكليوتيدات متتالية Translation involves switching from the nucleotide “language” to amino acid “language” تشتمل عملية الترجمة على التحول من ”لغة“ النيوكليوتيدات إلى ”لغة“ الأحماض الأمينية Each amino acid is specified by a codon يُختص كل حامض لأميني بشفرة خاصة به 64 codons are possible هناك 64 شفرة محتملة Some amino acids have more than one possible codon بعض الاحماض الأمينية لها أكثر من شفرة محتملة Comparing the linguistic meaning of transcription and translation is a useful analogy for the biochemical processes. Transcription involves staying in the nucleic acid language, while translation involves converting nucleotide codes into the amino acid language of proteins. I suggest that a student whose native language is not English may transcribe the words of an instructor during the lecture presentation, and then translate those words into his or her native language for better understanding. I also relate a story about purchasing a recipe book in French and not being able to make any of the dishes without translating the information into English! Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. Teaching Tips 1. The transcription of DNA into RNA is like a reporter who transcribes a political speech. In both situations, the language remains the same, although in the case of the reporter, it changes its form from spoken to written language. 2. The sequential information in DNA and RNA is analogous to the sequential information in the letters of a sentence. This analogy is also helpful when explaining the impact of insertion or deletion mutations that cause a shift in the reading frame (see Module 10.16). Copyright © 2009 Pearson Education, Inc.

Transcription & translations of codons
DNA molecule جزيء دنا Gene 1 جين 1 Transcription & translations of codons نسخ وترجمة وحدات الشفرة الوراثية Gene 2 جين 2 Gene 3 جين 3 DNA strand خيط الدنا Figure 10.7 Transcription and translation of codons. Transcription النسخ RNA الرنا Codon وحدة الشفرة Translation الترجمة Polypeptide متعدد البيبتيدات Amino acid حمض أميني

10.8 The genetic code is the Rosetta stone of life مواصفات الشفرة الوراثية هي بمثابة حجر رشيد* للحياة Characteristics of the genetic code مواصفات الشفرة الوراثية Triplet: Three nucleotides specify one amino acid ثلاثية: ثلاثة نيوكليوتيدات متتالية تختصص بحامض أميني واحد 61 codons correspond to amino acids تتطابق 61 شفرة مع الأحماض الأمينية AUG codes for methionine and signals the start of transcription تشفر AUG للميثايونين وتعطي إشارة البدء لعملية النسخ 3 “stop” codons signal the end of translation تعطي 3 شفرات ”توقف“ إشارة انهاء عملية الترجمة Exceptions to the universality of the genetic code are found for both mitochondrial and nuclear genes. In mitochondria from animals and microorganisms such as yeast, UGA codes for tryptophan rather than stop. In vertebrate mitochondria, AGA and AGG are stop codons instead of specifying arginine. In yeast mitochondria, all codons beginning with CU code for threonine instead of leucine, while the codons UUA and UUG still specify leucine. For the nuclear genes of the ciliated protozoan Tetrahymena thermophila, UAA and UAG code for glutamine rather than stop. Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. Teaching Tips 1. The authors note the parallel between the discovery in 1799 of the Rosetta stone, which provided the key that enabled scholars to crack the previously indecipherable hieroglyphic code, and the cracking of the genetic code in Consider challenging your students to explain what part of the genetic code is similar to the Rosetta stone. This could be a short in-class activity for small groups. 2. The authors note the universal use of the genetic code in all forms of life. The evolutionary significance of this fundamental, universal language is a reminder of the shared ancestry of all life. The universal genetic code is part of the overwhelming evidence for evolution. *حجر تم اكتشافه عام 1799 في بلدة رشيد بمصر يحمل نقوش متوازية باليونانية والهيروغليفية مما ساعد على حل رموز هذه الأخيرة Copyright © 2009 Pearson Education, Inc.

10.8 The genetic code is the Rosetta stone of life مواصفات الشفرة الوراثية هي بمثابة حجر رشيد* للحياة Redundant: More than one codon for some amino acids الترادف: قد يوجد أكثر من شفرة لبعض الأحماض الأمينية Unambiguous: Any codon for one amino acid does not code for any other amino acid عدم الغموض: أي شفرة لأي من الأحماض الأمينية لا تُستخدم لأي حامض أميني أخر Does not contain spacers or punctuation: Codons are adjacent to each other with no gaps in between لا تحتوي على فراغات أو علامات وقف: الشفرات ملتصقة ببعضها البعض بدون أي فراغات بينها Nearly universal العمومية والشمول ”تقريباً“ Exceptions to the universality of the genetic code are found for both mitochondrial and nuclear genes. In mitochondria from animals and microorganisms such as yeast, UGA codes for tryptophan rather than stop. In vertebrate mitochondria, AGA and AGG are stop codons instead of specifying arginine. In yeast mitochondria, all codons beginning with CU code for threonine instead of leucine, while the codons UUA and UUG still specify leucine. For the nuclear genes of the ciliated protozoan Tetrahymena thermophila, UAA and UAG code for glutamine rather than stop. Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. Teaching Tips 1. The authors note the parallel between the discovery in 1799 of the Rosetta stone, which provided the key that enabled scholars to crack the previously indecipherable hieroglyphic code, and the cracking of the genetic code in Consider challenging your students to explain what part of the genetic code is similar to the Rosetta stone. This could be a short in-class activity for small groups. 2. The authors note the universal use of the genetic code in all forms of life. The evolutionary significance of this fundamental, universal language is a reminder of the shared ancestry of all life. The universal genetic code is part of the overwhelming evidence for evolution. Copyright © 2009 Pearson Education, Inc.

Dictionary of the genetic code (RNA codons)
Second base First base Third base Figure 10.8A Dictionary of the genetic code (RNA codons). This listing of the codon “dictionary” can be used to illustrate the triplet and redundant nature of the code. While methionine and tryptophan have only one codon each, leucine, serine, and arginine each have six codons. It can also be pointed out that codons for the same amino acid often differ in the third nucleotide, a phenomenon described as “wobble.” The base pairing of the first two nucleotides of the codon with corresponding positions in the anticodon is stringent, but pairing of the third is weaker and more flexible. The wobble hypothesis proposed by Francis Crick allows for some nonstandard pairings that account for some of the redundancy of the genetic code. For example, if the third position of the codon is a U or C, it can pair with a G on the anticodon. This would mean that one tRNA, rather than two, could be used to translate UUU and UUC, for example. Estimates of 30–50 tRNAs necessary to pair with 61 codons are borne out by studies that identify 45 different tRNAs in some cell types. Dictionary of the genetic code (RNA codons) معجم الشفرة الوراثية ”شفرات الرنا“

Deciphering the genetic information in DNA
Strand to be transcribed الخيط المُعد للنسخ DNA Transcription النسخ Deciphering the genetic information in DNA حل شفرة المعلومات الوراثية في الدنا RNA Figure 10.8B Deciphering the genetic information in DNA. Start codon شفرة البدء Stop codon شفرة الانهاء Translation ترجمة Polypeptide متعدد البيبتيدات Met Lys Phe

10.16 Mutations can change the meaning of genes يمكن للطفرة أن تغير معني الجينات
A mutation is a change in the nucleotide sequence of DNA الطفرة هي تَغير في تسلسل نيوكليوتيدات الدنا Base substitutions: replacement of one nucleotide with another الاستعاضة القاعدية: استبدال نيوكليوتيد بأخر Effect depends on whether there is an amino acid change that alters the function of the protein يعتمد التأثير على ما إذا كان هناك حامض أميني يغير وظيفة البروتين أم لا Deletions or insertions: Alter the reading frame of the mRNA, so that nucleotides are grouped into different codons الحذف أو الإضافة يغير إطار القراءة للرنا المرسال, وبذلك يتم تجميع النيوكليوتيدات في شفرات مختلفة Lead to significant changes in amino acid sequence downstream of mutation تؤدي إلى تغيرات ملحوظة في تسلسل الأحماض الأمينية أسفل نقطة الطفرة Cause a nonfunctional polypeptide to be produced تؤدي إلى انتاج متعدد بيبتيدات عديم الفائدة Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. 2. Mutations are often discussed as part of evolution mechanisms. In this sense, mutations may be considered a part of a positive creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips 1. A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame, or words, are re-formed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. 2. The authors have noted elsewhere that “A random mutation is like a shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Copyright © 2009 Pearson Education, Inc.

10.16 Mutations can change the meaning of genes يمكن للطفرة أن تغير معني الجينات
Mutations can be يمكن أن تكون الطفرات Spontaneous: due to errors in DNA replication or recombination تلقائية: نتيجة لأخطاء في تضاعف أو الاتحادات الوراثية للدنا Induced by mutagens مستحدثة بالمُطفرات High-energy radiation الاشعاع عالى الطاقة Chemicals المواد الكيميائية Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. 2. Mutations are often discussed as part of evolution mechanisms. In this sense, mutations may be considered a part of a positive creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips 1. A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame, or words, are re-formed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. 2. The authors have noted elsewhere that “A random mutation is like a shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Copyright © 2009 Pearson Education, Inc.

* * The molecular basis of Sickle-cell disease
Normal hemoglobin DNA دنا الهيموجلوبين الطبيعي Mutant hemoglobin DNA دنا الهيموجلوبين الطافر * mRNA mRNA Normal hemoglobin الهيموجلوبين الطبيعي Sickle-cell hemoglobin هيموجلوبين الخلية المنجلية Figure 10.16A The molecular basis of sickle-cell disease. This figure shows the base pair change that leads to the formation of sickle cell hemoglobin. This results in an amino acid change in the protein, from glutamic acid to valine. This substitution of a hydrophobic amino acid for a hydrophilic one causes a significant difference in the activity of the -hemoglobin chain. Normal hemoglobin molecules exist as individual units whether they are bound to oxygen or not. Sickle cell hemoglobin molecules are also single entities when oxygen is bound, but they form large polymers that distort the shape of the cell when oxygen is released to the tissues. The cells may have an irregular appearance or assume the crescent or sickle shape for which the disease is named. These misshapen cells tend to clog blood vessels, leading to pain, infection, and damage to organs. Cells with sickle cell hemoglobin have a shorter lifetime than normal cells (10–20 days as opposed to 3 months) so anemia sets in because the bone marrow is unable to produce new cells as rapidly as they are removed from the population. This example demonstrates that a seemingly small change, a difference of one base pair leading to a change in a single amino acid (out of 147), can have severe effects. Glu * Val The molecular basis of Sickle-cell disease الأساس الجزيئي لمرض الخلية المنجلية

Types of mutations and their effects أنواع الطفرات وتأثيراتها المختلفة
Normal gene الجين الطبيعي mRNA Protein بروتين Met Lys Phe Gly Ala Base substitution الاستعاضة القاعدية Types of mutations and their effects أنواع الطفرات وتأثيراتها المختلفة Met Lys Phe Ser Ala Figure 10.16B Types of mutations and their effects. This figure contrasts the multiple amino acid changes caused by a deletion with the single amino acid change caused by a substitution. Base deletion الحذف القاعدي Missing حذف Met Lys Leu Ala His

Chapter 11 الباب الحادي عشر
How Genes Are Controlled كيفية التحكم في الجينات Lecture by Mary C. Colavito Translated by Nabih A. Baeshen 78

An operon is a group of genes under coordinated control in bacteria
11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes البروتينات المتفاعلة مع الدنا تُشغل أو تغلق جينات الكائنات أولية النواة استجابة لتغيرات بيئية Gene expression is the overall process of information flow from genes to proteins التعبير الجيني هي العملية الاجمالية لتدفق المعلومات من الجينات إلى البروتينات Mainly controlled at the level of transcription ويتم التحكم فيها عند مستوي النسخ A gene that is “turned on” is being transcribed to produce mRNA that is translated to make its corresponding protein ويقوم الجين الذي تم ”تشغيله“ بعملية النسخ لإنتاج الرنا المرسال الذي يتم ترجمته لبناء بروتينه المُطابق Organisms respond to environmental changes by controlling gene expression تستجيب الكائنات الحية للتغيرات البيئية عبر التحكم في التعبير الجيني An operon is a group of genes under coordinated control in bacteria الأوبارون عبارة عن مجموعة من الجينات تحت سيطرة تحكم مُنَسَق في البكتريا Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. 2. Mutations are often discussed as part of evolution mechanisms. In this sense, mutations may be considered a part of a positive creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips 1. A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame, or words, are re-formed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. 2. The authors have noted elsewhere that “A random mutation is like a shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Copyright © 2009 Pearson Education, Inc. 80

The lactose (lac) operon includesيشمل أوبارون اللاكتوز (
11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes البروتينات المتفاعلة مع الدنا تُشغل أو تغلق جينات الكائنات أولية النواة استجابة لتغيرات بيئية The lactose (lac) operon includesيشمل أوبارون اللاكتوز ( Three adjacent genes for lactose-utilization enzymes ثلاثة جينات متتالية تتحكم في بناء انزيمات الاستفادة من اللاكتوز Promoter sequence where RNA polymerase binds التسلسل المحفز حيث مكان ارتباط انزيم بلمرة الرنا Operator sequence is where a repressor can bind and block RNA polymerase action تسلسل المُشَغل حيث مكان ارتباك المثبط الذي يَحول دون عمل انزيم بلمرة الرنا Regulation of the lac operon التحكم في أوبارون اللاكتوز Regulatory gene codes for a repressor protein يشفر الجين المُنظم لبناء البروتين المثبط In the absence of lactose, the repressor binds to the operator and prevents RNA polymerase action في غياب اللاكتوز, يرتبط المثبط بالمُشغل ويَحُول دون عمل انزيم بلمرة الرنا Lactose inactivates the repressor, so the operator is unblocked يقوم اللاكتوز بتعطيل المُثبط, فيعمل المُشغل Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. 2. Mutations are often discussed as part of evolution mechanisms. In this sense, mutations may be considered a part of a positive creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips 1. A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame, or words, are re-formed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. 2. The authors have noted elsewhere that “A random mutation is like a shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Copyright © 2009 Pearson Education, Inc. 81

Types of operon control أنواع التحكم في الأوبارون
11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes البروتينات المتفاعلة مع الدنا تُشغل أو تغلق جينات الكائنات أولية النواة استجابة لتغيرات بيئية Types of operon control أنواع التحكم في الأوبارون Inducible operon (lac operon) الأوبارون المُستحث (أوبارون اللاكتوز) Active repressor binds to the operator يرتبط المُثبط النشط بالمُشغل Inducer (lactose) binds to and inactivates the repressor يرتبط المُستحث ”اللاكتوز) بالمثبط ويعمل على تعطيله Repressible operon (trp operon) الأوبارون المُثَبَط (أوبارون التريبتوفان) Repressor is initially inactive المُثبط بادئ ذي بدء مُعطل Corepressor (tryptophan) binds to the repressor and makes it active قرين المُثبط (الحامض الأميني التريبتوفان) يرتبط بالمثبط وينشطه For many operons, activators enhance RNA polymerase binding to the promoter بالنسبة للعديد من الأوبارونات, تقوي الناشطات عملية ارتباط انزيم بلمرة الرنا بالمُحفز Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. 2. Mutations are often discussed as part of evolution mechanisms. In this sense, mutations may be considered a part of a positive creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips 1. A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame, or words, are re-formed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. 2. The authors have noted elsewhere that “A random mutation is like a shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Copyright © 2009 Pearson Education, Inc. 82

Operon turned off (lactose absent) أوبارون مُعلق (غياب اللاكتوز)
Regulatory Gene الجين المُنظم Promoter Operator المُشغل المُحفز Lactose-utilization genes جينات الاستفادة من اللاكتوز DNA mRNA RNA polymerase cannot attach to promoter لا يستطيع انزيم بلمرة الرنا الارتباط بالمحفز Active repressor المُثَبط النشط Protein Operon turned off (lactose absent) أوبارون مُعلق (غياب اللاكتوز) DNA RNA polymerase bound to promoter انزيم بلمرة الرنا مرتبط بالمُشغل Figure 11.1B The lac operon. The lac operon is inducible, usually off, unless the inducer, lactose, is present. In the absence of lactose, active repressor binds to the operator and prevents transcription from the promoter sequence. It should be noted that small amounts of repressor are always present in the cell, since there is no operator region between the regulatory gene promoter (not shown) and the regulatory gene. The repressor binds reversibly to the operator region upstream of the lactose-utilization enzyme genes. When repressor is bound, RNA polymerase cannot initiate transcription from the promoter region. If lactose is present in the environment, some can diffuse into the cell and bind to free repressors, inactivating them. Inactivated repressors cannot bind to the operator region. Therefore, RNA polymerase can bind to the promoter and initiate transcription of the lactose-utilization enzyme genes. An mRNA with coding regions for all three genes is produced and then three separate proteins are translated from this mRNA. These proteins allow the cell to use lactose as an energy source. mRNA Protein Lactose Inactive repressor مُثبط مُعطل Enzymes for lactose utilization انزيمات الاستفادة من اللاكتوز Operon turned on (lactose inactivates repressor) أوبارون شغال (يعطل اللاكتوز المُثبط)

يشمل التمايز التخصص الخلوي، في كل من التركيب والوظيفة
11.2 Differentiation results from the expression of different combinations of genes ينتج التمايز من تعبير توافيق جينية مختلفة Differentiation involves cell specialization, in both structure and function يشمل التمايز التخصص الخلوي، في كل من التركيب والوظيفة Differentiation is controlled by turning specific sets of genes on or off يتم التحكم في التمايز بتشغيل أو غلق مجاميع خاصة من الجينات Gene expression control in Eukaryotes is brought about by turning specific sets of genes on or off يتم التحكم في التعبير الجيني في الكائنات حقيقية النواة بتشغيل أو غلق مجاميع خاصة من الجينات Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. 2. Mutations are often discussed as part of evolution mechanisms. In this sense, mutations may be considered a part of a positive creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips 1. A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame, or words, are re-formed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. 2. The authors have noted elsewhere that “A random mutation is like a shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Copyright © 2009 Pearson Education, Inc. 84

Regulatory proteins that bind to control sequences
11.5 Complex assemblies of proteins control eukaryotic transcription تجمعات معقدة من البروتينات تتحكم في عملية النسخ في الكائنات حقيقية النواة Regulatory proteins that bind to control sequences البروتينات المنظمة التي ترتبط بالتسلسلات التحكمية Transcription factors promote RNA polymerase binding to the promoter تحفز عوامل النسخ انزيم بلمرة الرنا للارتباط بالمحفز Activator proteins bind to DNA enhancers and interact with other transcription factors ترتبط الناشطات البروتينية بمقويات الدنا وتتفاعل مع عوامل النسخ الأخرى Silencers are repressors that inhibit transcription الكاتمات هي مثبطات تمنع عملية النسخ Control sequences تسلسلات التحكم Promoter المحفز Enhancerالمقوي Related genes located on different chromosomes can be controlled by similar enhancer sequences الجينات المرتبطة بعلاقات معينة فيما بينها والموجودة على كروموزومات مختلفة يمكن التحكم فيها بتسلسلات مقوية متشابهة Student Misconceptions and Concerns 1. Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. 2. Mutations are often discussed as part of evolution mechanisms. In this sense, mutations may be considered a part of a positive creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips 1. A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame, or words, are re-formed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. 2. The authors have noted elsewhere that “A random mutation is like a shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Copyright © 2009 Pearson Education, Inc. 85

A model for the turning on of a eukaryotic gene
Enhancers المقويات Promoter المحفز Geneجين DNA Activator Proteins بروتينات التنشيط Transcription factors عوامل النسخ Other proteins بروتينات أخرى RNA polymerase انزيم بلمرة الرنا Figure 11.5 A model for the turning on of a eukaryotic gene. Sequence of events: Activator proteins bind to an enhancer sequence. DNA bends to bring the enhancer sequence closer to the promoter region. Activators interact with other transcription factors that bind to the promoter. RNA polymerase is properly positioned on the promoter and transcription is initiated. Transcription عملية النسخ Bending of DNA انثناء الدنا A model for the turning on of a eukaryotic gene نموذج للتحكم في تشغيل إحدى الجينات في خلية حقيقية النواة

CLONING OF PLANTS AND ANIMALS استنساخ النباتات والحيوانات

Evidence is available from وهناك دلائل تشير إلى ذلك
11.14 Plant cloning shows that differentiated cells may retain all of their genetic potential يوضح استنساخ النبات أن الخلايا المتمايزة يمكنها الاحتفاظ بكل مخزونها الوراثي Most differentiated cells retain a full set of genes, even though only a subset may be expressed تحتفظ معظم الخلايا المتمايزة بكامل مجموعة جيناتها, حتى وإن تم التعبير عن مجموعة معينة فقط منها Evidence is available from وهناك دلائل تشير إلى ذلك Plant cloning (A root cell can divide to form an adult plant) استنساخ النبات (يمكن للخلية الجذرية أن تنقسم لتكون نبات بالغ) Animal limb regeneration إعادة توليد الأطراف الحيوانية Remaining cells divide to form replacement structures تنقسم الخلايا المتبقية لتكون تراكيب تعويضية Involved dedifferentiation followed by redifferentiation into specialized cells يلي ذلك التمايز إعادة التمايز للحصول على خلايا متخصصة Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. Teaching Tips 1. The basic question asked in Module is whether a cell becomes differentiated by selectively reading the genome or by retaining only the needed sections. In your course, you are unlikely to assign the entire Concepts textbook. Instead, you likely ask your students to selectively read chapters in the book. Students could remove all of the pages that they do not need, leaving only those that you have assigned. Students that keep their textbooks intact, reading only the assigned and relevant passages, behave like cells undergoing differentiation. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! Copyright © 2009 Pearson Education, Inc.

Root of carrot plant جذر نبات الجزر Single cell خلية واحدة Plantlet
Root cells cultured in nutrient medium استزراع خلايا جذرية في بيئة غذائية Cell division in culture الانقسام الخلوي في المزرعة Single cell خلية واحدة Plantlet نبتات صغيرة Adult plant النبات البالغ Figure Growth of a carrot plant from a differentiated root cell. This figure shows how an entire plant can be produced from a single root cell. Growth of a carrot plant from a differentiated root cell نمو نبات الجزر من خلية جذرية متمايزة

Nuclear transplantation زراعة النواة
11.15 Nuclear transplantation can be used to clone animals يمكن بزراعة النواة أن نقوم باستنساخ الحيوانات Nuclear transplantation زراعة النواة Replacing the nucleus of an egg cell or zygote with a nucleus from an adult somatic cell استبدال نواة الخلية البيضية أو اللاقحة بنواة من خلية جسدية بالغة Early embryo (blastocyst) can be used in يمكن استخدام الجنين المبكر (طور المُفلجة) لذلك الغرض Reproductive cloningالاستنساخ التكاثري Implant embryo in surrogate mother for development استزراع الجنين في الأم البديلة للتكوين الجنيني New animal is genetically identical to nuclear donor يكون الحيوان الجديد متماثل وراثياً مع نواة المعطي Therapeutic cloningالاستنساخ العلاجي Remove embryonic stem cells and grow in culture for medical treatments نقل الخلايا الجنينية الجذعية إلى مزرعة نسيجية لتنميتها لاستخدامها في العلاج الطبي Induce stem cells to differentiate تحفيز الخلايا الجذعية للتمايز Since nuclear transplantation requires both an egg and nuclear donor, the resulting cloned animal may have differences in mitochondrial genes, as these are derived from the egg donor. While nuclear changes related to differentiation were successfully reversed in producing Dolly, the chromosomes she received retained a significant characteristic from the donor adult that may have shortened her lifespan. These chromosomes were reduced in size, having lost DNA at the ends, or telomeres. The telomeres tend to shorten over successive cell divisions, as lagging strand synthesis may not be completed during DNA replication. Telomeres are repeated sequences that do not carry genes, but the loss can continue into the adjacent gene regions. Shortening of telomeres has been related to aging and to limiting of cell division. Dolly lived to about half her full life expectancy, contracting a contagious lung disease caused by a virus. It has been proposed that the shorter length of her chromosomes may have contributed to her reduced lifespan. For the Discovery Video Cloning, go to Animation and Video Files. For the BLAST Animation Stem Cells, go to Animation and Video Files. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. Teaching Tips 1. The researchers that cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity country singer Dolly Parton. 2. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The= cells that are removed are genetically analyzed while the remaining embryonic cell mass retains the potential to develop. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. Copyright © 2009 Pearson Education, Inc.

إزالة النواة من الخلية البيضيه Add somatic cell from adult donor
Donor Cell الخلية المعطية Nucleus from donor cell نواة الخلية المعطية Remove nucleus from egg cell إزالة النواة من الخلية البيضيه Add somatic cell from adult donor إضافة خلية جسدية من مُعطي بالغ Grow in culture to produce an early embryo (blastocyst) تنمو في مزرعة نسيجية لتنتج جنين مبكر (طور المفلجة) Reproductive Cloning الاستنساخ التكاثري Clone of donor is born المولود المُستنسخ من الخلية المعطيه Figure Nuclear transplantation for cloning. This figure distinguishes between reproductive and therapeutic cloning. Implant blastocyst in surrogate mother استزراع المفلجة في الأم البديلة Therapeutic Cloning الاستنساخ العلاجي Remove embryonic stem cells from blastocyst and grow in culture نقل الخلايا الجذعية الجنينية من المُفلجة وتنميتها في المزرعة النسيجية Induce stem cells to form specialized cells تحفيز الخلايا الجذعية لتكوين خلايا متخصصة

Chapter 12 الباب الثاني عشر
DNA Technology and Genomics تقنية الدنا ”التقنية الحيوية“ وشئون جينومية Lecture by Mary C. Colavito Translated by Nabih A. Baeshen

Recombinant DNA Techniques تقنيات الحمض النووي الاتحادي (المعاد اتحاده )
Gene splicing, which results in recombinant DNA, is one of the most exciting aspects of genetic engineering. أحد أكثر الجوانب المثيرة للهندسة الوراثية هو ربط الجينات الذى يؤدي إلى إعادة اتحاد الـ DNA. The DNA molecule can be cut at precise points and specific genes removed and transferred from one cell to another, even from such widely divergent species as plants beings and bacteria. جزيء الـ DNA يمكن أن يقطع في نقاط محددة وتنقل هذه الجينات من خلية إلى أخرى ، وتم هذا على نطاق واسع من الأنواع مثل النبات والبكتيريا.

Steps to produce a recombinant DNA in the colon bacteria E. Coli
(by genetic engineering technolog( خطوات انتاج DNA اتحادي (recombinant) في بكتيريا القولون E . Coli (تقنية الهندسة الوراثية) أ و A- Each E. coli cell contains one chromosome and several small circlets of DNA called plasmids. أ. كل خلية بكتيرية تحتوي على كروموزوم واحد وعدد من حلقات DNA الصغيرة المسماة بالبلازميدات (plasmids) B- The plasmids can be isolated from bacteria that have been ruptured ب. يمكن عزل البلازميدات من البكتيريا بعد تمزيق الجدار الخلوي. C- Restriction enzyme can break the plasmid at specific location ج. أحد الانزيمات المقصورة (Restriction enzyme) له القدرة على كسر البلازميد في نقطة معينة. D-The same restriction enzyme can be used to remove a segment of DNA –say the insulin gene-from a human cell. د. نفس الانزيم يمكن استخدامه لاقتطاع جزء معين من الـ DNA مثلاً الجين الموجه لإنتاج الانسولين من خلية إنسانية. E- The human gene is inserted into the E. coli plasmids by ligase enzyme and the result, is “recombinant” DNA. هـ. يتم إدخال الجين الانساني ببلازميد البكتيريا بواسطة الإنزيم اللاحم والنتيجة هي DNA اتحادي (recombinant) E. The recombinant plasmids can now be reinserted into E. coli cells where they will subsequently be reproduced, each time the bacterium divides. و. يمكن ادخال البلازميد في خلايا بكتيرية جديدة حيث يتضاعف تباعاً في كل انقسام بكتيري ويجعل البكتيريا تنتج الانسولين الانساني.

بعض منتجات البروتين من تقنية الدنا الاتحادي جدول 16.6
بعض منتجات البروتين من تقنية الدنا الاتحادي جدول 16.6 الاستخدام المصدر المنتج علاج داء السكري بكتريا القولون الانسولين البشري علاج قصور النمو هرمون النمو البشري علاج الحروق, القُرح ”القرحات“ عامل النمو الجلدي علاج ممكن للسرطان الانترلوكين -2 يساعد في تسمين الأبقار هرمون النمو البقري تحليل السيليولوز لإطعام الحيوانات انزيم هضم السيليولوز علاج لسرطان المبايض تاكسول علاج ممكن للسرطان والعدوى الفيروسية خميرة الخباز, بكتريا القولون انترفيرون (ألفا وجاما) الوقاية من الفيروسات الكبدية خميرة الخباز تطيعم فيروس الالتهاب الكبدي B علاج فقر الدم خلايا ثديية هرمون تكون الكريات الحمراء علاج نزيف الدم عامل VIII علاج نوبات القلب وبعض الجلطات القلبية منشط مولد بلازما الأنسجة Table 12.6 Some Protein Products of Recombinant DNA Technology.

Human insulin produced by bacteria أنسولين بشري مُنتج بواسطة البكتيريا
Figure 12.7A Human insulin produced by bacteria. Human insulin produced by bacteria أنسولين بشري مُنتج بواسطة البكتيريا 96

Transgenic organisms contain at least one gene from another species
12.8 CONNECTION: Genetically modified organisms are transforming agriculture رابطة تطبيقية: أحدثت الكائنات المُعدلة وراثياً نقله نوعية في مجال الزراعة Genetically modified (GM) organisms contain one or more genes introduced by artificial means تحتوي الكائنات المُعدلة وراثياً على جين أو أكثر والذي تم دمجه فيها صناعياً Transgenic organisms contain at least one gene from another species تحتوي الكائنات المُحورة على جين واحد على الأقل منقول إليها من كائن أخر GM plants (النباتات المُعدلة وراثياً ) Resistance to herbicides (مقاومة للمبيدات الزراعية) Resistance to pests (مقاومة للآفات) Improved nutritional profile (تحسن وضع المواد الغذائية ) GM animals (الحيوانات المُعدلة وراثياً ) Improved qualities (تحسين الجودة النوعية ) Production of proteins or therapeutics (انتاج البروتينات او المواد العلاجية) GM plants: Resistance to herbicides: Roundup Ready Soybeans contain a bacterial version of an amino acid synthesis enzyme that is less sensitive to glyphosate (Roundup). Resistance to pests: Bt corn produces an insect toxin, derived from the bacterium Bacillus thuringiensis. Improved nutritional profile: “Golden rice” has increased beta-carotene due to the presence of daffodil genes. GM animals: Improved qualities: Sheep with an extra copy of a growth hormone gene grow larger and faster and produce more milk and wool. Production of proteins or therapeutics: “Pharm” animals (see Module 12.6). The first GM organism approved for sale as food was the Flavr-Savr tomato. The modification was intended to prolong the shelf life of the tomato by keeping it from softening when ripe. Softening is caused by an enzyme called polygalacturonase that breaks down pectins in fruit. In the Flavr-Savr tomato, production of polygalacturonase was blocked by an antisense RNA molecule complementary to the enzyme’s mRNA. The shelf life of the tomato was indeed prolonged, but ultimately there was little flavor to savor as consumers found the fruit to have a bland taste! For Discovery Video Transgenics, go to Animation and Video Files. Student Misconceptions and Concerns 1. The genetic engineering of organisms can be controversial, creating various degrees of social unease and resistance. Yet, many debates about scientific issues are confused by misinformation. This provides an opportunity for you to assign students to take a position on such issues and support their arguments with accurate research. Students might debate whether a food or drug made from GM/transgenic organisms should be labeled as such, or discuss the risks and advantages of producing GM organisms. 2. The fact that the technologies described in this chapter can be used to swap genes between prokaryotes and eukaryotes reveals the fundamental similarities in genetic mechanisms shared by all forms of life. This very strong evidence of common descent provides proof of evolution that may be missed by your students. Teaching Tips 1. Roundup Ready Corn, a product of the agricultural biotechnology corporation Monsanto, is resistant to the herbicide Roundup. The general strategy for farmers is to spray fields of Roundup Ready corn with the herbicide Roundup, killing weeds but not the corn. A search of the Internet will quickly reveal the controversy associated with this and other genetically modified organisms (GMO), which can encourage interesting discussions and promote critical thinking skills. Module 12.9 discusses some of the issues related to the concerns over the use of GM organisms. Copyright © 2009 Pearson Education, Inc.

Chapter 8 الباب الثامن The Cellular Basis of الأساس الخلوي Reproductionللتكاثر and Inheritance والوراثة Lecture by Richard L. Myers.

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Chapter 8 الباب الثامن The Cellular Basis of الأساس الخلوي Reproductionللتكاثر and Inheritance والوراثة Lecture by Richard L. Myers.

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