BIO320-25&26as shown

BIO320-25&26as shown - Geneticdiversityinpopulations

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Genetic diversity in populations Text chapter 21; Question bank  E . Principles of population genetics -  why is there genetic polymorphism in populations? -  (how) do allele frequencies change over time? Human prehistory - written in our genes - reading the molecular clock -  origins of human genetic diversity -  are we still evolving? Genetics of quantitative and complex traits -  Is “heritability” real? useful? -  Genetic knowledge = genetic determinism?
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Applying Mendelian genetics to populations… 1. Calculating allele      genotype frequencies;  why allele frequencies don’t  change over time.  (Hardy-Weinberg-Castle equilibrium) 1.  change - mutation, selection, genetic drift Population genetics Questions: How much polymorphism in natural populations?  Why do lethal /deleterious mutations persist? Insights:    Evolution = change in allele frequencies over time “Molecular clock” - tracking prehistory in DNA  Text chapter 21; Question bank  E .
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A a A a 0.5 0.5 1. Genotype frequencies from allele frequencies AA aA Aa aa 0.25 0.25 0.25 0.25 A a 0.5 A a 0.5 A a A a A a a a A A 0.25 0.5 0.25 For 2 individuals But for a population….
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0 1 0 1 A a A a p q p q Genotype frequencies from allele frequencies A A A A a a a a a a A A A A a a a a a a ”gene pool” frequency  a q  =  1 - p   AA aA Aa aa p 2 pq pq q 2 AA aA Aa aa 2pq Genotype  frequencies in next  generation: p 2 q 2 frequency  A p where 0 < p < 1 a a AA AA a a a a A a A a
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Allele frequencies from genotype frequencies AA Aa aa = freq   AA  + 1/2 freq   Aa 2pq Substituting calculated genotype frequencies: p 2 q 2 frequency  A =  #   AA  + 1/2 #   Aa #  individuals  in population frequency  a = freq   aa  + 1/2 freq   Aa frequency  A  =   p 2   + 1/2 ( 2pq )   =   p 2   + pq Since  q = 1-p, =   p 2   + p(1-p)   =   p 2   + p -  p 2 =   p => Allele frequencies do not  change from one generation to the next. (Hardy/Weinberg/Castle equilibrium)
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Relation between allele and genotype frequencies 1 0 p Genotype  frequency frequency 1 0 q frequency a A a a AA A a 2pq - Most when p = q = 0.5   A a - Few when  q small   a a
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Two island populations- 10,000 40,000 a a AA Combined population a A p = 0.2 q = 0.8 A a after 1 generation AA a a 0.04 0.64 0.32 - Genotype frequencies reach HWC equilibrium in 1 generation same after n generations
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Example question Q. In a population at Hardy-Weinberg equilibrium, the frequency of people affected by a recessive Mendelian condition is 1/1600. What is the proportion of heterozygotes in the population? AA
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This note was uploaded on 09/12/2010 for the course AMS 316 taught by Professor Xing during the Spring '09 term at SUNY Stony Brook.

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BIO320-25&amp;amp;26as shown - Geneticdiversityinpopulations

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