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Gentics

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  • 1. Sources of Genetic Variability in Sexually Reproducing Organisms
  • 2. What produces genetic variety in groups of organisms that reproduce sexually?
    • The chromosomes independently line up and come together during Metaphase I. This is called Independent Assortment.
    • (The positioning of each homologous chromosome at Metaphase I is totally a matter of chance. Tetrads are assembled randomly AND the orientation of one tetrad does not impact the orientation of another tetrad.)
  • 3.  
  • 4.
    • Crossing over between homologous chromosomes during prophase I.
    • This occurs when portions of non-sister chromatids trade places.
  • 5.
    • Random fertilization of an egg by a sperm.
    • Let’s consider the following image…
  • 6. 2n = ? How many possible gamete combinations could meiosis possibly make from the cell?
  • 7. These are the possible gametes…
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  • 16. How do you calculate this? Is there a mathematical formula?
    • Yes!!
    • It is - number of possible gametes = 2 n
    • If 2n = 6; n = 3
    • That would be 2 3 = 8
    • How many different children could be made?
    • 8 possible ‘sperm cells’
    • x 8 possible ‘egg cells’
    • 64 possible genetically different children offspring
    • So, how many different gamete varieties is it possible for your body to make?...
  • 17.
    • 2n = 46 so n = …
    • n = 23 so 2 23 = …
    • 8,388,608 (million) – that’s just the number of different gametes your body could make using meiosis…
    • 8,388,608 (million) – that’s for your mate
    • You are 1 in 70,368,744,180,000 (trillion). That’s the number of genetically different children you and your spouse could make…
    • without crossing over…
  • 18. How many people have lived on earth since the beginning of time?
    • It is estimated that since Adam and Eve…
    • 110,000,000,000 (billion) people have lived on planet earth…
    • Why has sexual reproduction never produced your clone? (unless you’re an identical twin)
    • You are 1 in 70,368,744,180,000 (trillion).
  • 19.
    • You REALLY are one of a kind!! Your creator made you unique!!