Lec22_Drift&Migration - Flip the coin four times....

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Flip the coin four times. What is the probability of getting: 0 heads 0.0625 1 head 0.25 2 heads 0.375 3 heads 0.25 4 heads 0.0625 1 Flip the coin four times. Heads = A 1 allele. What is the probability of getting: 0 heads 0.0625 p = 0 1 head 0.25 p = 0.25 2 heads 0.375 p = 0.5 3 heads 0.25 p = 0.75 4 heads 0.0625 p = 1.0 1 highest probability outcome maintains p = 0.5 allele frequency, but certainly not guaranteed! = A1 p = f(A1) / 4 tosses 2 N = 4 N = 2 ind. Most likely outcome, p = 0.5 5 5657 568 5687 569 5697 56: 56:7 56; 5 8 9 : ; p = 0 0.25 0.5 0.75 1.0 2 N = 10 N = 5 ind. 5 5657 568 5687 569 5697 56: 5 8 9 : ; 7 < = > ? 85 p = 0 0.2 0.4 0.6 0.8 1.0
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 N = 10 N = 5 ind. 5 5657 568 5687 569 5697 56: 5 8 9 : ; 7 < = > ? 85 p = 0 0.2 0.4 0.6 0.8 1.0 Probability of 10% reduction: f(A1) ! 0.4 = 0.38 2 N = 100 N = 50 ind. 5 5658 5659 565: 565; 5657 565< 565= 565> 565? 5 < 89 8> 9; :5 :< ;9 ;> 7; <5 << =9 => >; ?5 ?< p = 0 0.2 0.4 0.6 0.8 1.0 Probability of 10% reduction: f(A1) ! 0.4 = 0.028 Are coin tosses a good model for real populations combining gametes through mating? As strange as it may seem – YES! Random mating is equivalent to random pairing of gametes drawn from the gene pool It might seem like any success of A 1 getting into the next generation at the expense of A 2 would be, by definition, differential reproductive success indicating selection. A change due to selection would require that the A 1 allele contribute to phenotypic differences determining fitness advantages in A 1 A 1 or A 1 A 2 genotypes. If true, expect consistent change in f(A 1 ) rather than erratic chance effects. Expect deviation from genetic drift theory @*.*A' B"(CD E*)F$ 2*) "*&0
Background image of page 2
allele freq p 0 1 0.6 0.4 0.2 0.8 In any population with finite size (any real population), genetic drift will change the frequency of an allele randomly over time. time allele freq p 0 1 0.6 0.4 0.2 0.8 In any population with finite size (any real population), genetic drift will change the frequency of an allele randomly over time. time allele freq p 0 1 0.6 0.4 0.2 0.8 In any population with finite size (any real population), genetic drift will change the frequency of an allele randomly over time. With two alleles, the other allele is changing in step because p + q = 1.0 time allele freq p 0 1 0.6 0.4 0.2 0.8 In any population with finite size (any real population), genetic drift will change the frequency of an allele randomly over time. Which allele is more likely to become fixed?
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 15

Lec22_Drift&amp;amp;Migration - Flip the coin four times....

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online