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Unit 3: Growth and Heredity Cells can grow only so big before they need to divide.

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Presentation on theme: "Unit 3: Growth and Heredity Cells can grow only so big before they need to divide."— Presentation transcript:

1 Unit 3: Growth and Heredity Cells can grow only so big before they need to divide

2 Mitosis (Cell Division) Mitosis nucleus divides into two nuclei number of chromosomes remain the same.

3 Mitosis Continuous process 4 Stages of Mitosis Prophase (1 st Phase) Chromosomes become visible Cell part that contains genes that express traits that is located in the nucleus Made up of thread-like material-chromatin Control cell processes and determine traits of the entire organisms Nuclear envelope dissolves Spindle forms (centrioles) Attach to chromosomes


5 Mitosis Metaphase (2 nd Phase) Chromosomes line up along the equator (middle of the cell)

6 Mitosis Anaphase (3 rd Phase) Centromeres divide ( connects the chromatids together) Chromatids are single strands of chromosomes Chromatids move toward opposite poles (spindle fibers are getting shorter)

7 Mitosis Telophase (4 th Phase) Nuclear envelope forms at each pole Chromosomes unwind Cytokinesis begins

8 Mitosis and Cytokinesis Cytokinesis-as mitosis ends this process begins Cytoplasm divides Forms two new cells End result of mitosis and cytokensis: 2 diploid (2n) identical cells

9 Cytokinesis: Plants and Animals Animals - cell pinches inward Plants - a new cell wall forms between the two new cells

10 The cell cycle is carefully controlled Checkpoints (traffic lights)-check for errors, correct mistakes and stop the process.

11 Mitosis Purpose: Replace old and worn out cells lost by wear and tear. Ex. Skin shedding Required to sustain life Immature human=growth Mitosis Type of Cells that divide in this process Body cells (hair, skin etc.)

12 Meiosis Process by which gametes (reproductive cell) are formed (egg and sperm cells) Sperm Cell-male reproductive cell Egg Cell- female reproductive cell Gametes contain half the number of chromosomes as body cells. Because offspring will get a copy of genes from each parent. Example: Female Gamete=23 chromosomes and Male Gamete=23- Zygote (fertilized egg has 46 chromosome)

13 Form of cellular division that halves the number of chromosomes Two cell divisions-meiosis I and II Total of eight phases Starts with homologous chromosomes are similar in shape and content End result: 4 haploid (n) genetically different cells.

14 Chromosomes Made up of thread like material (DNA) called chromatin (prophase) Located in the nucleus (control center of the cell) Control cell processes and determine the traits of the entire organisms (hair color, height, eye color etc.) Comprised of two sister chromatids (single strand of chromosomes) that are identical in content During cell division, each chromosome makes an exact copy of itself. Genes ( part of chromosome that controls inherited traits-eye color, height, etc.) are located on different parts of chromosome

15 Chromosome Structure (Draw)

16 Meiosis Graphic Organizer (Recopy) 2n nn n nn n MEIOISIS 1 MEIOISIS 2

17 Purpose of Meiosis Primary purpose is to increase genetic variations (differences)

18 Meiosis Provides Variations (Differences) 3 mechanisms contribute to genetic variations (Differences) Independent assortment, crossing-over and random fertilization

19 Independent Assortment Random distribution of homologous chromosomes during meiosis (genetic shuffling) Siblings look similar but different because they have some genes in common.

20 Random fertilization Only one sperm will fertilize an egg Each sperm carries a different combination of genes Allows for unlimited genetic combinations Only one sperm will enter the egg

21 Crossing Over Occurs in Prophase I Portion of one homologous chromosome is exchanged with a portion of another homologous chromosome

22 Importance of Genetic Variation Increases the speed of evolution (change) Allow favorable traits (thick fur) to pass from one generation to the next that increase chances of survival

23 Asexual Reproduction (Mitosis) Asexual reproduction-a single parent passes copies of all of its genes to each of its offspring Clone-organism that is genetically identical to its parent

24 Sexual Reproduction (Meiosis) Sexual reproduction-two parents each form haploid reproductive cells (sperm and egg), which join to form offspring. Have traits from both parents Not exactly like parents

25 Advantages of and Disadvantages of each type of reproduction Asexual reproduction: Disadvantage: lack of diversity that threatens the ability of the organisms to adapt in a changing environment Advantage: allows organisms to produce many offspring in a short period of time without using energy

26 Sexual Reproduction: Advantage: enables organism to adapt to changing environment Disadvantage: requires lots of energy and produce only a few organisms at a time.

27 Haploid (n) sperm Haploid (n) egg Diploid(2n) zygote

28 Venn Diagram: Asexual vs. Sexual Reproduction Insert the following terms into the right part of the circle. 1. one parent 2. two parents 3. clone 4. different from parent 5. requires more energy 6. difficulties adapting to a changing environment List two similarities in the middle Explain why genetic differences are important?

29 Heredity traits (characteristics of an organism) Many of your traits (characteristics of an organism)-eye color, hair color-resemble your parents. Inherited traits: traits that are passed from parents to their offspring. Eye Color Heredity-passing of traits from parents to offspring Study of heredity began with Gregor Mendel Genetics-focuses on heredity


31 Mendels Studies Based his hypotheses on pea plants Concluded the following: 1. An individual inherits two copies of a gene-one from each parent

32 Mendels Theories 2. There are alternative versions of genes Ex. Flower Color: purple and white

33 Mendels Theories 3. Some traits are expressed and others are hidden. Dominant: gene whose trait always shows itself Recessive: gene of a trait that is hidden when the dominant gene is present.

34 Mendels findings in modern terms Homozygous-two alleles are the same Ex. AA or aa Heterozygous-two alleles are different Ex. Aa Heterozygous only dominant trait is expressed Ex. F=freckles f=no freckles Ff=

35 Mendels findings in modern terms Genotype-set of alleles (letters) ex. Ff Phenotype is the physical appearance ex. Freckles

36 Mendels Ideas Give Rise to the Laws of Heredity Law of segregation- Alleles for a trait separate when gametes are formed. Alleles These allele pairs are then randomly united at fertilization (uniting of the egg and sperm to form zygote (fertilized egg)fertilization


38 Studying Heredity Punnett Squares-chart that shows possible gene combinations Organisms have at least two genes for most traits. An uppercase letter represents a dominant trait A lowercase letter represents a recessive trait

39 Mini Lab Follow procedures found on p. 281 Answer analysis questions after completing the punnett square problems.

40 Left Side Divide page into six and define the following terms: Homozygous, heterozygous, phenotype, genotype, dominant and recessive For each term complete the following: Definition, drawing, and sentence using the term correctly (put sentence in a box).

41 Acquired Traits vs. Inherited Traits Acquired Traits are traits that you learn because of the environment that you live in. Example: favorite color or favorite food Inherited Traits are traits that are passed from generation to generation by genes inherited from your parents. Ex. Eye color, hair color.

42 Non-Mendelian Patterns of Inheritance All human traits are determined by 23 pair (46 chromosomes) of chromosomes. 23 rd pair are not alike Males=XY Females=XX The X and Y chromosome determine gender (male or female) All eggs contain X chromosomes Sperm cell can contain either a X or Y chromosome Gender is inherited (determined) from the father

43 Sex-Linked Trait Sex-Linked Traits-traits that are inherited along with gender. X chromosomes carries many genes Y chromosome carries few genes Most genes for sex-linked traits are found on the X chromosome. Sex-linked disorders are found more often in men than women. Most genes for sex-linked disorder is recessive Men only have one X chromosome If they inherit trait they will have the disorder.

44 Patterns of Heredity Polygenic trait-traits that are influenced by several genes. Ex. Hair color, skin color, weight, height, and eye color

45 Intermediate traits Incomplete dominance- pattern of inheritance in which alleles from both parents are blended. Ex. red flower is crossed with white flower-offspring pink flowers


47 Traits with two forms Co-dominance- pattern of inheritance in which both alleles of a gene is expressed. Ex: Both red and white will be displayed on the flower

48 Jumping Genes (Genetic Variation) Genes that move around or jump around and relocate. Create new genetic combinations Only take place on certain genes (wouldnt want your heart genes jumping around and relocating)

49 DNA Blueprint of the organism Controls everything about the way that you look( color of your eyes to width of your feet) Transfers characteristics from one generation to the next

50 The structure of DNA Watson and Crick determined the structure of DNA Three dimensional model DNA Double helix-two strands twisted around each other like a winding staircase Each strand is made of linked nucleotides Made up of three parts: phosphate group, a five-carbon sugar, and a nitrogen-containing base. Five carbon sugar: deoxyribose

51 Structure of DNA. 4 Nitrogen bases- adenine(A), guanine(G), thymine(T), and cytosine(C) Double helix is held together by weak hydrogen bonds

52 Base Pair Rule Rule that explains how nitrogen bases pair up on the DNA molecule A (adenine) pairs with (T) Thymine Guanine (G) pairs with Cytosine (C) Build a DNA Molecule

53 The Replication of DNA Takes place in interphase Process of making a copy of DNA 1.DNA molecule unzips between nitrogen bases 2.New nitrogen bases pair up and attach to each half of the ladder. 3.Two new DNA strands that are exact copies of the original DNA molecule /molgenetics/dna-rna2.swf /molgenetics/dna-rna2.swf

54 Checking for errors DNA polymerase: proofread role Corrects mistakes in nucleotide bases

55 Left Side Assignment Write an analogy story that relates to each step of DNA replication. Each paragraph should relate to each step of replication. Step 1: something unzips Step 2: something is added Step 3: a copy is made This should be written in color.

56 Expression of Traits Traits such as eye color are determined by proteins Specific instructions are found on DNA Proteins are not built directly from DNA Too large to fit through the nuclear pores

57 RNA Is a special molecule that is used to make proteins Ribonucleic Acid (RNA) Different from DNA in many ways Single stranded Has a new nitrogen base: uracil Does not have thymine Different sugar: ribose

58 From Genes to Proteins Gene Expression Step one: instruction are transferred from DNA to RNA molecule in process called transcription Step Two: Translation (takes place in cytoplasm)-process in which cell uses two different RNA molecules to read the instructions on the RNA and put together the amino acids that make up proteins tRNA: transfers the amino acids to the ribosome's site of protein synthesis

59 The Genetic Code is Written in Three-Nucleotide Words Codons-series of three-nucleotide sequences on the mRNA (messenger RNA) that translate into the amino acids that make proteins. EX. AUC codes for the amino acid_______

60 From Genes to Proteins SIMPLY PUT: DNA makes RNA makes Proteins make traits( such as eye color, skin color and hair color)

61 Mutations Any change in an organisms genetic material. Can be harmful if it decreases the organisms ability to function properly. Abnormalities can be detected in a karyotype. A photo of the chromosomes


63 Two Types of Mutations Gene Mutations: result from changes in a single gene Chromosomal Mutations: involve changes in an entire chromosome. Deletion- a piece of a chromosome breaks off Duplication-two copies of a certain set of genes

64 Point Mutations Change in one or just a few nucleotides Sickle Cell Anemia is caused by this type of mutation.

65 Mutations Cont. Mutations in gametes (egg and sperm) can be passed on from generation to generation. Color blindness Mutations in body cells (somatic cells) affect only one individual. Lung cancer

66 Down Syndrome (Mutation) Caused by extra copy of 21 st chromosome (non-disjunction- when one or more chromosomes fail to separate) Individuals with this condition Short stature, a round face, and varying degrees of mental retardation.


68 Mutations External influences can create mutations. Mutations can be caused by exposure to specific chemicals or radiation Example: Lung Cancer Chemicals found in the cigarettes cause mutations in lung cells. Example: Skin Cancer Ultraviolet Rays cause mutations in skin cells.

69 Lung Cancer

70 Skin Cancer

71 Detecting Genetic Disorders Most can not be cured. Persons with family history may wish to undergo genetic counseling. Genetic Counseling- medical guidance that informs people about genetic problems that could affect them or their offspring.

72 Genetic Engineering Methods used to produce new forms of DNA. Involves building NEW DNA by taking genes from one species and inserting them into a completely different species. Examples of Genetically Engineered Items 1. Tomatoes with elephant genes (make the tomatoes grow larger)

73 Benefits of Genetic Engineering Medicines to treat disease such as diabetes. Identify individuals and establish relationships -DNA fingerprinting

74 Benefits of Genetic Engineering Add favorable characteristics to a plant Resistant to pest or pesticides Tolerate harsh environmental conditions such as drought


76 Benefits of Genetic Engineering Improve farm animals Cows that produce more milk (more productive) Make medically useful proteins for humans Produce transplant organs for humans


78 Disadvantages Experimenting with Bacteria can cause new diseases with no cure. Federal Government regulates experiments because of danger.

79 Questions Create three questions and a two sentence summary for your notes. Make sure you write your questions next to the answer in the notes. Make one of your questions a How?

80 Snappy Products You are a design team for a small biotechnology company. Your Job is a follows: 1. Brainstorm a list a ways that you can improve popcorn. Ex. Popcorn that pops faster 2. Think of something else that has the desired trait that you want to see in your popcorn. 3. Combine the solution that you thought of in #2 with popcorn, make the the popcorn that can solve the problem that you mentioned in #1. Assignment: Draw your new popcorn product, be sure to clearly show what other product that you combined with your popcorn to create something new. Create a catchy name for you product Write a tune with words to be used to as a radio commercial. Include your price in your song.

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