1. © 2013 Pearson Education, Inc. Lectures by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition – Eric J. Simon, Jean L. Dickey, and Jane B. Reece Chapter 8 Cellular Reproduction: Cells from Cells

2. Biology and Society: Virgin Birth of a Dragon In 2002, zookeepers at the Chester Zoo were surprised to discover that their Komodo Dragon laid eggs. –The female dragon had not been in the company of a male. –The eggs developed without fertilization, in a process called parthenogenesis. –DNA analysis confirmed that her offspring had genes only from her. © 2013 Pearson Education, Inc.

3. Biology and Society: Virgin Birth of a Dragon A second European Komodo dragon is now known to have reproduced –asexually, via parthenogenesis, and –sexually. © 2013 Pearson Education, Inc.

4. Figure 8.0

5. WHAT CELL REPRODUCTION ACCOMPLISHES Reproduction –may result in the birth of new organisms but –more commonly involves the production of new cells. When a cell undergoes reproduction, or cell division, two “daughter” cells are produced that are genetically identical –to each other and –to the “parent” cell. © 2013 Pearson Education, Inc.

6. Before a parent cell splits into two, it duplicates its chromosomes, the structures that contain most of the cell’s DNA. During cell division, each daughter cell receives one identical set of chromosomes from the lone, original parent cell. WHAT CELL REPRODUCTION ACCOMPLISHES © 2013 Pearson Education, Inc.

7. Cell division plays important roles in the lives of organisms. Cell division –replaces damaged or lost cells, –permits growth, and –allows for reproduction. WHAT CELL REPRODUCTION ACCOMPLISHES © 2013 Pearson Education, Inc.

8. Figure 8.1a Cell Replacement Growth via Cell Division FUNCTIONS OF CELL DIVISION Human kidney cell Early human embryo LM Colorized SEM

9. In asexual reproduction, –single-celled organisms reproduce by simple cell division and –there is no fertilization of an egg by a sperm. Some multicellular organisms, such as sea stars, can grow new individuals from fragmented pieces. Growing a new plant from a clipping is another example of asexual reproduction. WHAT CELL REPRODUCTION ACCOMPLISHES © 2013 Pearson Education, Inc.

10. Figure 8.1b Asexual Reproduction FUNCTIONS OF CELL DIVISION Regeneration of a sea star LM Division of an amoeba Growth of a clipping

11. In asexual reproduction, the lone parent and its offspring have identical genes. Mitosis is the type of cell division responsible for –asexual reproduction and –growth and maintenance of multicellular organisms. WHAT CELL REPRODUCTION ACCOMPLISHES © 2013 Pearson Education, Inc.

12. Sexual reproduction requires fertilization of an egg by a sperm using a special type of cell division called meiosis. Thus, sexually reproducing organisms use –meiosis for reproduction and –mitosis for growth and maintenance. WHAT CELL REPRODUCTION ACCOMPLISHES © 2013 Pearson Education, Inc.

13. In a eukaryotic cell, –most genes are located on chromosomes in the cell nucleus and –a few genes are found in DNA in mitochondria and chloroplasts. THE CELL CYCLE AND MITOSIS © 2013 Pearson Education, Inc.

14. Eukaryotic Chromosomes Each eukaryotic chromosome contains one very long DNA molecule, typically bearing thousands of genes. The number of chromosomes in a eukaryotic cell depends on the species. © 2013 Pearson Education, Inc.

15. Figure 8.2 Number of chromosomes in body cells Indian muntjac deer Species Opossum Koala Human Mouse Giraffe Buffalo Dog Red viscacha rat Duck-billed platypus 102 78 60 54 46 40 30 22 16 6

16. Chromosomes are –made of chromatin, fibers composed of roughly equal amounts of DNA and protein molecules and –not visible in a cell until cell division occurs. Eukaryotic Chromosomes © 2013 Pearson Education, Inc.

17. Figure 8.3 Chromosomes LM

18. Figure 8.4 Duplicated chromosomes (sister chromatids) TEM Tight helical fiber Thick supercoil TEM Centromere Nucleosome “Beads on a string” Histones DNA double helix

19. Before a cell divides, it duplicates all of its chromosomes, resulting in two copies called sister chromatids containing identical genes. Two sister chromatids are joined together tightly at a narrow “waist” called the centromere. Eukaryotic Chromosomes © 2013 Pearson Education, Inc.

20. When the cell divides, the sister chromatids of a duplicated chromosome separate from each other. Once separated, each chromatid is –considered a full-fledged chromosome and –identical to the original chromosome. Eukaryotic Chromosomes © 2013 Pearson Education, Inc.

21. Figure 8.5 Chromosome duplication Sister chromatids Chromosome distribution to daughter cells

22. The Cell Cycle A cell cycle is the ordered sequence of events that extend –from the time a cell is first formed from a dividing parent cell –to its own division into two cells. The cell cycle consists of two distinct phases: 1. interphase and 2. the mitotic phase. © 2013 Pearson Education, Inc.

23. Figure 8.6 Cytokinesis (division of cytoplasm) Mitosis (division of nucleus) Mitotic (M) phase: cell division (10% of time) Interphase: metabolism and growth (90% of time) S phase (DNA synthesis; chromosome duplication) G1G1 G2G2

24. Most of a cell cycle is spent in interphase. During interphase, a cell –performs its normal functions, –doubles everything in its cytoplasm, and –grows in size. The Cell Cycle © 2013 Pearson Education, Inc.

25. The mitotic (M) phase includes two overlapping processes: 1.mitosis, in which the nucleus and its contents divide evenly into two daughter nuclei and 2.cytokinesis, in which the cytoplasm is divided in two. The Cell Cycle © 2013 Pearson Education, Inc.

26. Mitosis consists of four distinct phases: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Mitosis and Cytokinesis © 2013 Pearson Education, Inc.

27. Figure 8.7a Nuclear envelope Plasma membrane Chromosome (two sister chromatids) Spindle microtubules Fragments of nuclear envelope Centrosome Centromere Early mitotic spindle Centrosomes (with centriole pairs) Chromatin PROPHASE INTERPHASE

28. Figure 8.7b ANAPHASE METAPHASE TELOPHASE AND CYTOKINESIS Spindle Daughter chromosomes Cleavage furrow Nuclear envelope forming

29. Cytokinesis usually –begins during telophase, –divides the cytoplasm, and –is different in plant and animal cells. Mitosis and Cytokinesis © 2013 Pearson Education, Inc.

30. In animal cells, cytokinesis –is known as cleavage and –begins with the appearance of a cleavage furrow, an indentation at the equator of the cell. Mitosis and Cytokinesis © 2013 Pearson Education, Inc.

31. Figure 8.8a Cleavage furrow Cleavage furrow Contracting ring of microfilaments Daughter cells SEM

32. In plant cells, cytokinesis begins when vesicles containing cell wall material collect at the middle of the cell and then fuse, forming a membranous disk called the cell plate. Mitosis and Cytokinesis © 2013 Pearson Education, Inc.

33. Figure 8.8b Daughter cells New cell wall Vesicles containing cell wall material Cell plate Cell wall Wall of parent cell Cell plate forming Daughter nucleus LM

34. Cancer Cells: Growing Out of Control Normal plant and animal cells have a cell cycle control system that consists of specialized proteins, which send “stop” and “go-ahead” signals at certain key points during the cell cycle. © 2013 Pearson Education, Inc.

35. What Is Cancer? Cancer is a disease of the cell cycle. Cancer cells do not respond normally to the cell cycle control system. Cancer cells can form tumors, abnormally growing masses of body cells. If the abnormal cells remain at the original site, the lump is called a benign tumor. © 2013 Pearson Education, Inc.

36. The spread of cancer cells beyond their original site of origin is metastasis. Malignant tumors can –spread to other parts of the body and –interrupt normal body functions. A person with a malignant tumor is said to have cancer. What Is Cancer? © 2013 Pearson Education, Inc.

37. Figure 8.9 A tumor grows from a single cancer cell. Cancer cells invade neighboring tissue. Metastasis: Cancer cells spread through lymph and blood vessels to other parts of the body. Glandular tissue Blood vessel Tumor Lymph vessels

38. Sexual reproduction –depends on meiosis and fertilization and –produces offspring that contain a unique combination of genes from the parents. MEIOSIS, THE BASIS OF SEXUAL REPRODUCTION © 2013 Pearson Education, Inc.

39. Figure 8.10

40. Homologous Chromosomes Different individuals of a single species have the same –number and –types of chromosomes. A human somatic cell –is a typical body cell and –has 46 chromosomes. © 2013 Pearson Education, Inc.

41. A karyotype is an image that reveals an orderly arrangement of chromosomes. Homologous chromosomes –are matching pairs of chromosomes that –can possess different versions of the same genes. Homologous Chromosomes © 2013 Pearson Education, Inc.

42. Figure 8.11 Pair of homologous chromosomes LM One duplicated chromosome Centromere Sister chromatids

43. Humans have –two different sex chromosomes, X and Y, and –22 pairs of matching chromosomes, called autosomes. Homologous Chromosomes © 2013 Pearson Education, Inc.

44. Gametes and the Life Cycle of a Sexual Organism The life cycle of a multicellular organism is the sequence of stages leading from the adults of one generation to the adults of the next. © 2013 Pearson Education, Inc.

45. Figure 8.12 Multicellular diploid adults (2n  46) MEIOSIS FERTILIZATION MITOSIS 2n2n and development Key Sperm cell n n Diploid zygote (2n  46) Diploid (2n) Haploid (n) Egg cell Haploid gametes (n  23)

46. Humans are diploid organisms with –body cells containing two sets of chromosomes and –haploid gametes that have only one member of each homologous pair of chromosomes. In humans, a haploid sperm fuses with a haploid egg during fertilization to form a diploid zygote. Gametes and the Life Cycle of a Sexual Organism © 2013 Pearson Education, Inc.

47. Sexual life cycles involve an alternation of diploid and haploid stages. Meiosis produces haploid gametes, which keeps the chromosome number from doubling every generation. Gametes and the Life Cycle of a Sexual Organism © 2013 Pearson Education, Inc.

48. Figure 8.13-3 MEIOSIS I Sister chromatids separate. MEIOSIS II Homologous chromosomes separate. INTERPHASE BEFORE MEIOSIS Sister chromatids Duplicated pair of homologous chromosomes Chromosomes duplicate. Pair of homologous chromosomes in diploid parent cell 1 2 3

49. The Process of Meiosis In meiosis, –haploid daughter cells are produced in diploid organisms, –interphase is followed by two consecutive divisions, meiosis I and meiosis II, and –crossing over occurs. © 2013 Pearson Education, Inc.

50. Figure 8.14a MEIOSIS I : HOMOLOGOUS CHROMOSOMES SEPARATE Sister chromatids remain attached Pair of homologous chromosomes INTERPHASE Sister chromatids Homologous chromosomes pair up and exchange segments. Chromosomes duplicate. Pairs of homologous chromosomes line up. Pairs of homologous chromosomes split up. Nuclear envelope Chromatin Centromere Microtubules attached to chromosome Sites of crossing over Spindle Centrosomes (with centriole pairs) PROPHASE I METAPHASE I ANAPHASE I

51. Figure 8.14b TELOPHASE II AND CYTOKINESIS Sister chromatids separate ANAPHASE II Cleavage furrow TELOPHASE I AND CYTOKINESIS Two haploid cells form; chromosomes are still doubled. MEIOSIS II : SISTER CHROMATIDS SEPARATE PROPHASE II METAPHASE II Haploid daughter cells forming During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing single chromosomes.

52. Review: Comparing Mitosis and Meiosis In mitosis and meiosis, the chromosomes duplicate only once, during the preceding interphase. The number of cell divisions varies: –Mitosis uses one division and produces two diploid cells. –Meiosis uses two divisions and produces four haploid cells. All the events unique to meiosis occur during meiosis I. © 2013 Pearson Education, Inc.

53. Figure 8.15 Duplicated chromosome MITOSIS Prophase Chromosomes align. Metaphase Sister chromatids separate. Anaphase Telophase 2n2n Prophase I Metaphase I Anaphase I Telophase I MEIOSIS MEIOSIS I Site of crossing over Homologous pairs align. Homologous chromosomes separate. Sister chromatids separate. Haploid n  2 MEIOSIS II Parent cell n MEIOSIS I 2n2n nn n

54. The Origins of Genetic Variation Offspring of sexual reproduction are genetically different from their parents and one another. © 2013 Pearson Education, Inc.

55. Independent Assortment of Chromosomes When aligned during metaphase I of meiosis, the side-by-side orientation of each homologous pair of chromosomes is a matter of chance. Every chromosome pair orients independently of all of the others at metaphase I. For any species, the total number of chromosome combinations that can appear in the gametes due to independent assortment is –2 n, where n is the haploid number. © 2013 Pearson Education, Inc.

56. For a human, –n = 23. –With n = 23, there are 8,388,608 different chromosome combinations possible in a gamete. Independent Assortment of Chromosomes © 2013 Pearson Education, Inc.

57. Random Fertilization A human egg cell is fertilized randomly by one sperm, leading to genetic variety in the zygote. If each gamete represents one of 8,388,608 different chromosome combinations, at fertilization, humans would have 8,388,608 × 8,388,608, or more than 70 trillion different possible chromosome combinations. So we see that the random nature of fertilization adds a huge amount of potential variability to the offspring of sexual reproduction. © 2013 Pearson Education, Inc.

58. Figure 8.17 Colorized LM

59. What happens when errors occur in meiosis? Such mistakes can result in genetic abnormalities that range from mild to fatal. When Meiosis Goes Awry © 2013 Pearson Education, Inc.

60. How Accidents during Meiosis Can Alter Chromosome Number In nondisjunction, –the members of a chromosome pair fail to separate at anaphase, –producing gametes with an incorrect number of chromosomes. Nondisjunction can occur during meiosis I or II. © 2013 Pearson Education, Inc.

61. Figure 8.20-3 Meiosis I Abnormal Gametes Homologous chromosomes fail to separate. Meiosis II Sister chromatids fail to separate. Abnormal Normal n n n  1 n – 1 n  1 n – 1 NONDISJUNCTION IN MEIOSIS I NONDISJUNCTION IN MEIOSIS II

62. If nondisjunction occurs, and a normal sperm fertilizes an egg with an extra chromosome, the result is a zygote with a total of 2n + 1 chromosomes. If the organism survives, it will have –an abnormal karyotype and –probably a syndrome of disorders caused by the abnormal number of genes. How Accidents during Meiosis Can Alter Chromosome Number © 2013 Pearson Education, Inc.

63. Figure 8.21 Abnormal egg cell with extra chromosome Normal sperm cell n  1 n (normal) Abnormal zygote with extra chromosome 2n  1

64. Down Syndrome: An Extra Chromosome 21 Down syndrome –is also called trisomy 21, –is a condition in which an individual has an extra chromosome 21, and –affects about one out of every 700 children. © 2013 Pearson Education, Inc.

65. Figure 8.22 Trisomy 21 LM

66. The incidence of Down syndrome in the offspring of normal parents increases markedly with the age of the mother. Down Syndrome: An Extra Chromosome 21 © 2013 Pearson Education, Inc.

67. Figure 8.23 Age of mother 25 35 45 20 30 40 50 10 0 20 30 40 50 60 70 80 90 Infants with Down syndrome (per 1,000 births)

68. Figure 8.UN02 Duplicated chromosome Chromosome (one long piece of DNA) Centromere Sister chromatids

69. Figure 8.UN03 Interphase Cell growth and chromosome duplication G2G2 Mitotic (M) phase S phase DNA synthesis; chromosome duplication G1G1 Genetically identical “daughter” cells Cytokinesis (division of cytoplasm) Mitosis (division of nucleus)

70. Figure 8.UN04 MITOSIS Male and female diploid adults (2n  46) MEIOSIS Sperm cell Human Life Cycle Key Haploid (n) Diploid (2n) Haploid gametes (n  23) Egg cell Diploid zygote (2n  46) and development FERTILIZATION 2n2n n n

71. Figure 8.UN05 Daughter cells Parent cell (2n) MITOSIS Chromosome duplication 2n2n2n2n MEIOSIS MEIOSIS I Parent cell (2n) Chromosome duplication Daughter cells n MEIOSIS II Pairing of homologous chromosome Crossing over n nn

72. Figure 8.UN06 (a) (b) (c) (d) LM

73. Chapter 9 Patterns of Inheritance

74. People have selected and mated dogs with preferred traits for more than 15,000 years. Over thousands of years, such genetic tinkering has led to the incredible variety of body types and behaviors in dogs today. The biological principles underlying genetics have only recently been understood. Biology and Society: Our Longest-Running Genetic Experiment: Dogs © 2013 Pearson Education, Inc.

75. Figure 9.0

76. Heredity is the transmission of traits from one generation to the next. Genetics is the scientific study of heredity. Gregor Mendel –worked in the 1860s, –was the first person to analyze patterns of inheritance, and –deduced the fundamental principles of genetics. HERITABLE VARIATION AND PATTERNS OF INHERITANCE © 2013 Pearson Education, Inc.

77. Figure 9.1

78. In an Abbey Garden Mendel studied garden peas because they –were easy to grow, –came in many readily distinguishable varieties, –are easily manipulated, and –can self-fertilize. © 2013 Pearson Education, Inc.

79. A character is a heritable feature that varies among individuals. A trait is a variant of a character. Each of the characters Mendel studied occurred in two distinct traits. In an Abbey Garden © 2013 Pearson Education, Inc.

80. Mendel –created purebred varieties of plants and –crossed two different purebred varieties. In an Abbey Garden © 2013 Pearson Education, Inc.

81. Hybrids are the offspring of two different purebred varieties. –The parental plants are the P generation. –Their hybrid offspring are the F 1 generation. –A cross of the F 1 plants forms the F 2 generation. In an Abbey Garden © 2013 Pearson Education, Inc.

82. Mendel’s Law of Segregation Mendel performed many experiments. He tracked the inheritance of characters that occur as two alternative traits. © 2013 Pearson Education, Inc.

83. Figure 9.4 White Purple Recessive Dominant Green Yellow Terminal Axial Wrinkled Round Green Yellow Seed shape Seed color Flower position Flower color Pod color Recessive Dominant Pod shape Stem length Inflated Constricted Tall Dwarf

84. Figure 9.4a

85. Monohybrid Crosses A monohybrid cross is a cross between purebred parent plants that differ in only one character. © 2013 Pearson Education, Inc.

86. Figure 9.5-3 Purple flowers F 1 Generation White flowers P Generation (purebred parents) All plants have purple flowers F 2 Generation Fertilization among F 1 plants (F 1  F 1 ) of plants have purple flowers of plants have white flowers 3 4 1 4

87. Figure 9.5a

88. Mendel developed four hypotheses from the monohybrid cross, listed here using modern terminology (including “gene” instead of “heritable factor”). 1. The alternative versions of genes are called alleles. Monohybrid Crosses © 2013 Pearson Education, Inc.

89. 2. For each inherited character, an organism inherits two alleles, one from each parent. –An organism is homozygous for that gene if both alleles are identical. –An organism is heterozygous for that gene if the alleles are different. Monohybrid Crosses © 2013 Pearson Education, Inc.

90. 3. If two alleles of an inherited pair differ, –then one determines the organism’s appearance and is called the dominant allele and –the other has no noticeable effect on the organism’s appearance and is called the recessive allele. Monohybrid Crosses © 2013 Pearson Education, Inc.

91. 4. Gametes carry only one allele for each inherited character. –The two alleles for a character segregate (separate) from each other during the production of gametes. –This statement is called the law of segregation. Monohybrid Crosses © 2013 Pearson Education, Inc.

92. Do Mendel’s hypotheses account for the 3:1 ratio he observed in the F 2 generation? A Punnett square highlights –the four possible combinations of gametes and –the four possible offspring in the F 2 generation. Monohybrid Crosses © 2013 Pearson Education, Inc.

93. Figure 9.6 P GenerationGenetic makeup (alleles) Alleles carried by parents Gametes Purple flowers PP White flowers pp All P All p p P F 1 Generation (hybrids) F 2 Generation (hybrids) Alleles segregate Gametes Purple flowers All Pp 2 1 2 1 Sperm from F 1 plant Eggs from F 1 plant Phenotypic ratio 3 purple : 1 white Genotypic ratio 1 PP : 2 Pp : 1 pp p p P P PPPp pp

94. Geneticists distinguish between an organism’s physical appearance and its genetic makeup. –An organism’s physical appearance is its phenotype. –An organism’s genetic makeup is its genotype. Monohybrid Crosses © 2013 Pearson Education, Inc.

95. Genetic Alleles and Homologous Chromosomes A gene locus is a specific location of a gene along a chromosome. Homologous chromosomes have alleles (alternate versions) of a gene at the same locus. © 2013 Pearson Education, Inc.

96. Figure 9.7 Homologous chromosomes P Genotype: Gene loci P a aa b B Dominant allele Recessive allele Bb PP Homozygous for the dominant allele Homozygous for the recessive allele Heterozygous with one dominant and one recessive allele a

97. Mendel’s Law of Independent Assortment A dihybrid cross is the mating of parental varieties differing in two characters. What would result from a dihybrid cross? Two hypotheses are possible: 1. dependent assortment or 2. independent assortment. © 2013 Pearson Education, Inc.

98. Figure 9.8 F 1 Generation F 2 Generation RRYY Predicted results (not actually seen) P Generation Gametes RY rryy ry (a) Hypothesis: Dependent assortment RrYy RY ry Sperm Eggs RY ry Actual results (support hypothesis) RRYY RY rryy ry RrYy (b) Hypothesis: Independent assortment Gametes RY ry Sperm RY ry Ry rY Ry rY RRYY Rryy RRyy RrYy RRYy RrYy rrYy Rryy rryy RrYY rrYYRrYyrrYy RRYy RrYy Yellow round Yellow wrinkled Green wrinkled Green round 16 1 3 3 9 4 1 4 1 4 1 4 1 4 1 4 1 4 1 4 1 2 1 2 1 2 1 2 1

99. Figure 9.12 DOMINANT TRAITS Free earlobe RECESSIVE TRAITS Widow’s peakFreckles Attached earlobe Straight hairline No freckles

100. A family pedigree –shows the history of a trait in a family and –allows geneticists to analyze human traits. Family Pedigrees © 2013 Pearson Education, Inc.

101. Figure 9.13 Female Male Attached Free Female Male First generation (grandparents) Second generation (parents, aunts, and uncles) Third generation (brother and sister) Aaron Ff Betty Ff Cletus ff Debra Ff Evelyn FF or Ff Lisa FF or Ff Fred ff Gabe ff Hal Ff Ina Ff Jill ff Kevin ff

102. Human Disorders Controlled by a Single Gene Many human traits –show simple inheritance patterns and –are controlled by single genes on autosomes. © 2013 Pearson Education, Inc.

103. Table 9.1

104. Recessive Disorders Most human genetic disorders are recessive. Individuals who have the recessive allele but appear normal are carriers of the disorder. © 2013 Pearson Education, Inc.

105. Figure 9.16 Parents Sperm Eggs d Dwarf D Dd d dd d Normal (no achondroplasia) Molly Jo Dwarf (achondroplasia) Dd dd Normal dd Normal Dwarf Matt Amy Jacob Zachary Jeremy

106. Genetic Testing Today many tests can detect the presence of disease-causing alleles. Most genetic tests are performed during pregnancy. –Amniocentesis collects cells from amniotic fluid. –Chorionic villus sampling removes cells from placental tissue. Genetic counseling helps patients understand the results and implications of genetic testing. © 2013 Pearson Education, Inc.

107. The Role of Environment Many human characters result from a combination of –heredity and –environment. Only genetic influences are inherited. © 2013 Pearson Education, Inc.

108. Figure 9.29b Colorized SEM Y X

109. Sex Determination in Humans Nearly all mammals have a pair of sex chromosomes designated X and Y. –Males have an X and Y. –Females have XX. © 2013 Pearson Education, Inc.

110. Sex-Linked Genes Any gene located on a sex chromosome is called a sex-linked gene. –Most sex-linked genes are found on the X chromosome. –Red-green colorblindness is –a common human sex-linked disorder and –caused by a malfunction of light-sensitive cells in the eyes. © 2013 Pearson Education, Inc.

111. Hemophilia –is a sex-linked recessive blood-clotting trait that may result in excessive bleeding and death after relatively minor cuts and bruises and –has plagued the royal families of Europe. Sex-Linked Genes © 2013 Pearson Education, Inc.

112. Figure 9.UN08

113. Chapter 10 The Structure and Function of DNA

114. DNA: STRUCTURE AND REPLICATION DNA –was known to be a chemical in cells by the end of the nineteenth century, –has the capacity to store genetic information, and –can be copied and passed from generation to generation. The discovery of DNA as the hereditary material ushered in the new field of molecular biology, the study of heredity at the molecular level. © 2013 Pearson Education, Inc.

115. DNA and RNA Structure DNA and RNA are nucleic acids. –They consist of chemical units called nucleotides. –A nucleotide polymer is a polynucleotide. –Nucleotides are joined by covalent bonds between the sugar of one nucleotide and the phosphate of the next, forming a sugar-phosphate backbone. © 2013 Pearson Education, Inc.

116. Figure 10.1 Sugar-phosphate backbone Phosphate group Nitrogenous base DNA nucleotide Thymine (T) Sugar Polynucleotide DNA double helix Sugar (deoxyribose) Phosphate group Nitrogenous base (can be A, G, C, or T)

117. The sugar in DNA is deoxyribose. Thus, the full name for DNA is deoxyribonucleic acid. DNA and RNA Structure © 2013 Pearson Education, Inc.

118. The four nucleotides found in DNA differ in their nitrogenous bases. These bases are –thymine (T), –cytosine (C), –adenine (A), and –guanine (G). RNA has uracil (U) in place of thymine. DNA and RNA Structure © 2013 Pearson Education, Inc.

119. Watson and Crick’s Discovery of the Double Helix James Watson and Francis Crick determined that DNA is a double helix. Watson and Crick used X-ray crystallography data to reveal the basic shape of DNA. Rosalind Franklin produced the X-ray image of DNA. © 2013 Pearson Education, Inc.

120. Figure 10.3a James Watson (left) and Francis Crick

121. The model of DNA is like a rope ladder twisted into a spiral. –The ropes at the sides represent the sugar- phosphate backbones. –Each wooden rung represents a pair of bases connected by hydrogen bonds. Watson and Crick’s Discovery of the Double Helix © 2013 Pearson Education, Inc.

122. Figure 10.4 Twist

123. DNA bases pair in a complementary fashion: –adenine (A) pairs with thymine (T) and –cytosine (C) pairs with guanine (G). Watson and Crick’s Discovery of the Double Helix © 2013 Pearson Education, Inc.

124. Figure 10.5 (c) Computer model (b) Atomic model (a) Ribbon model Hydrogen bond

125. DNA Replication When a cell reproduces, a complete copy of the DNA must pass from one generation to the next. Watson and Crick’s model for DNA suggested that DNA replicates by a template mechanism. © 2013 Pearson Education, Inc.

126. Figure 10.6 Parental (old) DNA molecule Daughter (new) strand Daughter DNA molecules (double helices) Parental (old) strand

127. DNA can be damaged by X-rays and ultraviolet light. DNA polymerases –are enzymes, –make the covalent bonds between the nucleotides of a new DNA strand, and –are involved in repairing damaged DNA. DNA Replication © 2013 Pearson Education, Inc.

128. DNA replication ensures that all the body cells in multicellular organisms carry the same genetic information. DNA Replication © 2013 Pearson Education, Inc.

129. DNA replication in eukaryotes –begins at specific sites on a double helix (called origins of replication) and –proceeds in both directions. DNA Replication © 2013 Pearson Education, Inc.

130. Figure 10.7 Origin of replication Origin of replication Origin of replication Parental strands Parental strand Daughter strand Two daughter DNA molecules Bubble

131. THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN DNA provides instructions to –a cell and –an organism as a whole. © 2013 Pearson Education, Inc.

132. How an Organism’s Genotype Determines Its Phenotype An organism’s genotype is its genetic makeup, the sequence of nucleotide bases in DNA. The phenotype is the organism’s physical traits, which arise from the actions of a wide variety of proteins. © 2013 Pearson Education, Inc.

133. DNA specifies the synthesis of proteins in two stages: 1. transcription, the transfer of genetic information from DNA into an RNA molecule and 2. translation, the transfer of information from RNA into a protein. How an Organism’s Genotype Determines Its Phenotype © 2013 Pearson Education, Inc.

134. Figure 10.8-3 DNA Cytoplasm Nucleus RNA Protein TRANSCRIPTION TRANSLATION

135. From Nucleotides to Amino Acids: An Overview Genetic information in DNA is –transcribed into RNA, then –translated into polypeptides, –which then fold into proteins. © 2013 Pearson Education, Inc.

136. What is the language of nucleic acids? –In DNA, it is the linear sequence of nucleotide bases. –A typical gene consists of thousands of nucleotides in a specific sequence. When a segment of DNA is transcribed, the result is an RNA molecule. RNA is then translated into a sequence of amino acids in a polypeptide. From Nucleotides to Amino Acids: An Overview © 2013 Pearson Education, Inc.

137. Figure 10.10 Amino acid RNA TRANSCRIPTION DNA strand Polypeptide Codon Gene 1 Gene 3 Gene 2 DNA molecule TRANSLATION

138. Experiments have verified that the flow of information from gene to protein is based on a triplet code. A codon is a triplet of bases, which codes for one amino acid. From Nucleotides to Amino Acids: An Overview © 2013 Pearson Education, Inc.

139. The Genetic Code The genetic code is the set of rules that convert a nucleotide sequence in RNA to an amino acid sequence. Of the 64 triplets, –61 code for amino acids and –3 are stop codons, instructing the ribosomes to end the polypeptide. © 2013 Pearson Education, Inc.

140. Figure 10.11 Second base of RNA codon First base of RNA codon Phenylalanine (Phe) Leucine (Leu) Cysteine (Cys) Leucine (Leu) Isoleucine (Ile) Valine (Val) Met or start Serine (Ser) Proline (Pro) Threonine (Thr) Tyrosine (Tyr) Histidine (His) Glutamine (Gln) Asparagine (Asn) Alanine (Ala) Stop Glutamic acid (Glu) Aspartic acid (Asp) Lysine (Lys) Arginine (Arg) Tryptophan (Trp) Arginine (Arg) Serine (Ser) Glycine (Gly) Third base of RNA codon UUU UUC UUA UUG UAU UAC CAU CAC CAA CAG AAU AAC AAA AAG GAU GAC GAA GAG UGU UGC AGU AGC AGA AGG GGU GGC GGA GGG CGU CGC CGA CGG GCU GCC GCA GCG ACU ACC ACA ACG CCU CCC CCA CCG UCU UCC UCA UCG CUU CUC CUA CUG GUU GUC GUA GUG AUU AUC AUA AUG UAA UAG UGA UGG UCAG U C A G UCAGUCAG UCAGUCAG UCAGUCAG UCAGUCAG

141. Because diverse organisms share a common genetic code, it is possible to program one species to produce a protein from another species by transplanting DNA. The Genetic Code © 2013 Pearson Education, Inc.

142. Figure 10.12

143. Transcription: From DNA to RNA Transcription –makes RNA from a DNA template, –uses a process that resembles the synthesis of a DNA strand during DNA replication, and –substitutes uracil (U) for thymine (T). © 2013 Pearson Education, Inc.

144. Transcription: From DNA to RNA RNA nucleotides are linked by the transcription enzyme RNA polymerase. © 2013 Pearson Education, Inc.

145. Figure 10.13 Newly made RNA RNA nucleotides RNA polymerase Template strand of DNA Direction of transcription (a) A close-up view of transcription (b) Transcription of a gene RNA polymerase Completed RNA Growing RNA Termination Initiation Terminator DNA Elongation RNA Promoter DNA RNA polymerase DNA of gene 213

146. Initiation of Transcription The “start transcribing” signal is a nucleotide sequence called a promoter, which is –located in the DNA at the beginning of the gene and –a specific place where RNA polymerase attaches. The first phase of transcription is initiation, in which –RNA polymerase attaches to the promoter and –RNA synthesis begins. © 2013 Pearson Education, Inc.

147. RNA Elongation During the second phase of transcription, called elongation, –the RNA grows longer and –the RNA strand peels away from its DNA template. © 2013 Pearson Education, Inc.

148. Termination of Transcription During the third phase of transcription, called termination, –RNA polymerase reaches a special sequence of bases in the DNA template called a terminator, signaling the end of the gene, –polymerase detaches from the RNA and the gene, and –the DNA strands rejoin. © 2013 Pearson Education, Inc.

149. The Processing of Eukaryotic RNA In the cells of prokaryotes, RNA transcribed from a gene immediately functions as messenger RNA (mRNA), the molecule that is translated into protein. The eukaryotic cell –localizes transcription in the nucleus and –modifies, or processes, the RNA transcripts in the nucleus before they move to the cytoplasm for translation by ribosomes. © 2013 Pearson Education, Inc.

150. Translation: The Players Translation is the conversion from the nucleic acid language to the protein language. © 2013 Pearson Education, Inc.

151. Messenger RNA (mRNA) Translation requires –mRNA, –ATP, –enzymes, –ribosomes, and –transfer RNA (tRNA). © 2013 Pearson Education, Inc.

152. Transfer RNA (tRNA) –acts as a molecular interpreter, –carries amino acids, and –matches amino acids with codons in mRNA using anticodons, a special triplet of bases that is complementary to a codon triplet on mRNA. © 2013 Pearson Education, Inc.

153. Figure 10.15 tRNA polynucleotide (ribbon model) Anticodon Hydrogen bond Amino acid attachment site tRNA (simplified representation) RNA polynucleotide chain

154. Ribosomes Ribosomes are organelles that –coordinate the functions of mRNA and tRNA and –are made of two subunits. Each subunit is made up of –proteins and –a considerable amount of another kind of RNA, ribosomal RNA (rRNA). © 2013 Pearson Education, Inc.

155. Ribosomes A fully assembled ribosome holds tRNA and mRNA for use in translation. © 2013 Pearson Education, Inc.

156. Figure 10.16 Next amino acid to be added to polypeptide Growing polypeptide tRNA mRNA tRNA binding sites Codons Ribosome (b) The “players” of translation (a) A simplified diagram of a ribosome Large subunit Small subunit P site mRNA binding site A site

157. Review: DNA  RNA  Protein In a cell, genetic information flows from –DNA to RNA in the nucleus and –RNA to protein in the cytoplasm. © 2013 Pearson Education, Inc.

158. Figure 10.20-6 Transcription RNA polymerase mRNA DNA Intron Nucleus mRNA Intron Tail Cap RNA processing tRNA Amino acid Amino acid attachment Enzyme ATP Initiation of translation Ribosomal subunits Termination Anticodon Codon Elongation Polypeptide Stop codon Anticodon A 346521

159. As it is made, a polypeptide –coils and folds and –assumes a three-dimensional shape, its tertiary structure. Transcription and translation are how genes control the structures and activities of cells. Review: DNA  RNA  Protein © 2013 Pearson Education, Inc.

160. Mutations A mutation is any change in the nucleotide sequence of DNA. Mutations can change the amino acids in a protein. Mutations can involve –large regions of a chromosome or –just a single nucleotide pair, as occurs in sickle-cell disease. © 2013 Pearson Education, Inc.

161. Figure 10.21 Normal hemoglobin DNA mRNA Normal hemoglobin Mutant hemoglobin DNA mRNA Sickle-cell hemoglobin Glu Val

162. Mutations within a gene can be divided into two general categories: 1.nucleotide substitutions (the replacement of one base by another) and 2.nucleotide deletions or insertions (the loss or addition of a nucleotide). Insertions and deletions can –change the reading frame of the genetic message and –lead to disastrous effects. Types of Mutations © 2013 Pearson Education, Inc.

163. Figure 10.22 mRNA and protein from a normal gene Deleted (a) Base substitution Inserted (b) Nucleotide deletion (c) Nucleotide insertion MetLysPheGlyAla MetLysPheSerAla MetLysLeuAla MetLysLeuTrpArg

164. Figure 10.22a mRNA and protein from a normal gene (a) Base substitution MetLysPhe Gly Ala Met LysPhe Ser Ala

165. Figure 10.22b mRNA and protein from a normal gene Deleted (b) Nucleotide deletion MetLysLeuAla MetLysPhe Gly Ala

166. Figure 10.22c mRNA and protein from a normal gene MetLysPhe Gly Ala (c) Nucleotide insertion MetLysLeuTrpArg Inserted

167. Mutagens Mutations may result from –errors in DNA replication or recombination or –physical or chemical agents called mutagens. Mutations –are often harmful but –are useful in nature and the laboratory as a source of genetic diversity, which makes evolution by natural selection possible. © 2013 Pearson Education, Inc.

168. Figure 10.23

169. Figure 10.UN03a Polynucleotide Phosphate group Nucleotide Sugar DNA Nitrogenous base

170. Figure 10.UN03b Nitrogenous base Number of strands Sugar DNA RNA Ribose Deoxy- ribose CGATCGAT CGAUCGAU 1 2

171. Figure 10.UN04 New daughter strand Parental DNA molecule Identical daughter DNA molecules

172. Figure 10.UN05 Polypeptide TRANSCRIPTION mRNA DNA Gene TRANSLATION

173. Figure 10.UN06 Growing polypeptide mRNA Codons Large ribosomal subunit tRNA Small ribosomal subunit Anticodon Amino acid

174. Figure 10.UN07