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Week 7 w_answers

Week 7 w_answers - BICD 100 Genetics Smith TA Kjeld Kjeld...

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Kjeld Aamodt [email protected] Office Hours: Thursday, 11-11:50 at Clics 1st floor/ patio Sections: A04 & B07 @ 3010A Thursday, 10-10:50 am , 12-12:50 pm Genetics -- Week 7 Population Genetics: Hardy-Weinberg Equilibrium conditions: 1. __ random mating _________ 2. ___ no migration _________ 3. ___ no mutation ___________ 4. __ no selection for / against any genotype _ 5. ____ large population _______ Equations ( on Final ) Population Genetics Basics f(A) = p f(a) = q p + q = 1 f(AA) + f(Aa) + d(aa) = 1 p = f(A) = f(AA) + 1/2 f(Aa) q = f(a) = f(aa) + 1/2 f(Aa) If mating is random, f(AA) = p 2 f(Aa) = 2pq f(aa) = q 2 so p 2 + 2pq +q 2 = 1 Selection Against a Recessive Trait W is fitness - for fittest genotype = 1; W is for lethal genotype = 0 s (selection co-efficient) = 1 - W For a recessive mutation under negative selection (ie., W for AA and Aa = 1, but W for aa < 1): After one round of selection, q ʼ = (q - sq 2 )/(1 - sq 2 ) Mutation Rate of conversion of A --> a is μ (mutation rate) q ʼ = q + μ p Δ q max = μ p Mutation/Selection Balance (Equilibrium) Recessive mutation (where W for AA and Aa = 1 but W for aa <1) q equilib = ( μ /s) (where s is the selection co-efficient for aa) Overdominance (where Aa is fittest genotype, ie., W for Aa > W for AA or aa) P equilib = s 2 / (s 1 + s 2 ) and q equilib = s 1 / (s 1 + s 2 ) (where s 1 is selection co-efficient for AA and s 2 for aa) Migration Let p m = f(A) for migrants and p i = f(A) for initial population before arrival of migrants Let p = f(A) for new population made when migrants join initial population If m is the proportion of individuals in the new population that were migrants, p ʼ = mp m + (1 - m)p i Δ p = m(p m - p i ) --> --> m = (p ʼ - p i )/(p m - p i ) Non-Random Mating F is the inbreeding co-efficient = probability of being homozygous by descent f(aa) = qF + q 2 (1 - F) f(Aa) = 2pg(1 - F) f(AA) = pF + p 2 (1 - F) F for a population = 1 - (H/2pg) where H is the actual frequency of heterozygotes F = (1/2)N
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