Human Heredity and Development_Walsh_Date_022310

Human Heredity and Development_Walsh_Date_022310 - Lecture...

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Overview We have 23 pairs of chromosomes. We have sister – held by a centimeter. In meiosis – produce gametes (23 chromosomes) to continue species. Gametes are half-loid. There’s 46 in total. First division of separation is (2) separating sister chromodids which end up in 4 haploids MEIOSIS CONTRIBUTES TO GENETIC DIVERSITY How? o Random/Independent assortment - we deal with a simple situation with 2n = 6 chromosomes so there’s 3 pairs of chromosomes; each pair sets up their own pair without afflicting other pairs; they’re all independent. Not all happening in the same cell but are all undergoing meiosis with 4 different possibilities. o There’s a formula we use: if there are 3 pairs of chromosomes, -- 2³ = 8 different gamete o With 23 pairs, it would be 2^23 different gametes are possible = 8,388,608 o 2^n – number of different gametes o N = number of homologous pairs o Genetic diversity – 8 million different female gametes X 0 8 million male gametes = 70 trillion genetically unique individuals
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Human Heredity and Development_Walsh_Date_022310 - Lecture...

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