Biology 3300- Non-Random Mating

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BIOL 2200
Theresa Burg

Biology 3300 Jan.31 , 2013 Non-Random Mating Two types: 1) Assortative mating: individuals choose to mate with individuals with a specific phenotype which may be the same phenotype or a different one - Ex: snow geese - Color morphs - Offspring will imprint on what their parent looks like o If the offspring see blue eggs they will mate with blue geese when they grow up - B__ = blue bb = white o Blue was found in the East and white in the West o Some areas experienced some mixing o Even though there may be white in the blue population, the blue will still mate with blue because of imprinting - Active decision with mating 2) Inbreeding - Selfing in plants - Mating with relatives (consanguineous similar blood) - Inbreeding can be a function of how big the population is - Can also have lots of populations with low densities so mate choice can be somewhat limited - There is less choice in mating Inbreeding Coefficient F - Probability that two alleles are identical by descent - F = 0  no breeding - F = 0.5  selfing Homozygote: AA = i i1-F)i+ pF i Heterozygote: AA =i2jp(1-Fi j - P and p are frequencies of I and j allele i j 1/2 1/2 (1/2) = 1/16 Probabilities: multiply “AND” add “OR” - Circles are girls, squares are boys - F = probability of red OR blue 1/2 1/2 o F = 1/16 + 1/16 = 1/8 o F = 1/8 = 0.125 What is the inbreeding coefficient of their offspring? 1/2 1/2 = (1/2) = 1/16 = (1/2) = 1/16 4 = (1/2) = 1/16 1/2 1/2 = (1/2) = 1/16 F = 1/16 + 1/16 + 1/16 + 1/16 = ¼ = 0.25 There is a 50% chance that the orange triangle will be passed on from each parent each generation Inbreeding Depression ( ϭ) Ϭ = 1 – (ws/w 0 W s fitness of selfed individuals W 0 fitness of outcrossed - A value of 1 is a lot of inbreeding - A value closer to 0 there is no difference between the selfed individuals and the outcrossed - Easiest to measure when individual is stressed - Appear later in life o Maternal effect? o Seed has ample resources, created by mother, no stress early on because they have everything they need - Varies among lineages o Allele dependent Does inbreeding change genotype frequencies? Allele frequencies? - All individuals reproduce by selfing - 1:2:1 ratio in generation 0
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