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Genetic Variation LHS Biology B
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Sexual and Asexual Reproduction
Organisms produce offspring in 2 different ways Sexual reproduction requires 2 parents Asexual reproduction only requires 1 parent Most organisms use one or the other, but some can do both
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Sexual Reproduction 2 parents’ genes combine to form a genetically unique offspring Genetic variation comes from mutation, meiosis, and random fertilization Usually takes more energy than asexual reproduction Most organisms that you are most familiar with use sexual reproduction Mammals, reptiles, birds, fish, amphibians, and many plants
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Asexual Reproduction 1 parent produces a genetic copy of itself
Genetic Variation comes from mutation only Usually takes less energy and time than sexual reproduction Some organisms that can use asexual reproduction are: bacteria, some plants, sea stars, and hydra
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Summary Disadvantages: Slower Takes more energy More complicated
Sexual Reproduction Asexual Reproduction Disadvantages: Slower Takes more energy More complicated Rare organisms Major Advantage Genetic Variation Disadvantage: Little genetic variation Advantages: Faster Saves Energy Less Complicated Only 1 parent required
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What type of reproduction?
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Meiosis A type of cell division that produces reproductive cells
The cells produced are haploid, but come from a diploid parent cell Diploid: A cell with 2 sets of chromosomes, one from each parent Haploid: A cell with only one set of chromosomes
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Meiosis
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Results of Meiosis Produces 4 haploid cells called gametes
Reproductive cells, sperm, egg 2 gametes (1 sperm and 1 egg) come together at fertilization, resulting in a zygote This keeps the chromosome number from changing each generation
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Cell Division: Meiosis I
Diploid: 4 chromosomes Cell Division: Meiosis I Cell Division: Meiosis II Haploid: 2 chromosomes
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Meiosis is different from Mitosis
2 Divisions: Meiosis I and Meiosis II Daughter cells are genetically unique Different from each other and the original cell Only occurs in certain organs of sexually reproducing organisms
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Challenge Question #1 Is Meiosis happening in your body right now?
Is Mitosis happening in your body right now? Explain :)
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How to Keep them Straight
MiTOsis happens in TOES Produces identical body cells MeIosis is why I am unique, why I am ME Produces unique gametes
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Chromosomes Review
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Meiosis I Pairs of chromosomes are divided
One chromosome from each pair goes to each daughter cell Produces cells with the haploid number of chromosomes Each daughter cell gets one chromosome from each pair The pairs split up randomly
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Meiosis I Diploid: 4 chromosomes Diploid: 4 chromosomes
Haploid: 2 chromosomes Haploid: 2 chromosomes
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Meiosis II Results in 4 haploid daughter cells Basically like mitosis
Chromotids seperate at the centromere like mitosis Results in 4 haploid daughter cells 4 functional sperm 1 functional egg and 3 nonfunctional haploid cells (called polar bodies)
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Challenge Question #2 Explain the purpose of Meiosis in just a few sentences.
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Meiosis II Diploid: 4 chromosomes Diploid: 4 chromosomes
Haploid: 2 chromosomes Meiosis II Haploid: 2 chromosomes
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Fertilization Random Fertilization
Joining of egg and sperm to produce a zygote Zygote is a diploid cell Random Fertilization Any sperm is equally likely to fertilize any egg Another source of genetic variation
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Challenge Question #3 Draw and label a picture that models the process of meiosis.
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Discovery of DNA DNA is the genetic material that makes up chromosomes
When it is not condensed it is called chromatin It wasn’t that long ago that we didn’t know about DNA See timeline on page 292 World War II lasted from 1939 to 1949 for reference
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Image Credits Bruce the shark: ucetheshark.jpg Sven the Reindeer: ages/8/83/SVEN2.png Aphie and the Queen: mages/e/eb/Queenbugslife.png Bacteria: Strawberry plant: Hydra: Simmons/pages/hydra2.htm Sea Star: armed-sea-critter.html
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Image Credits Continued
Meiosis Diagram 1: Mitosis & Meiosis side by side: cellcycle-mitosis-meiosis Chromosomes: htm Meiosis I: /bio%20101%20lectures/meiosis/meiosis.htm Meiosis II: czi5F0idF74/UFySnBEmB5I/AAAAAAAAAXM/MjWg4VsX34I/s640/Meio sis+II.jpg Telophase II/Cytokinesis: k4/4webimages/figure photo.jpg Anaphase II: k4/4webimages/figure photo.jpg Fertilization:
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