Lecture 7 - Non-random mating

Lecture 7 - Non-random mating - 1 The Neutral Theory, Part...

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The Neutral Theory, Part 3: Variation within populations Equilibrium heterozygosity H ˆ ) 1 4 ( 4 + μ N N ; - if 4 N μ is small then H ˆ 4 N μ . In the context of molecular population genetics, H ˆ is often called θ . - Note that H ˆ is proportional to μ . - Taken together, these two relationships imply that both the amount of neutral divergence between taxa, k, and the amount of neutral polymorphism within species, H should be proportional - IF NOT? i) Selection (locus specific) ii) Neutral mutation rate not the same (in part a function of N e ) Lecture 7 - Non-Random Mating and its Consequences - Mating is usually not random (even in self-fertile hermaphrodites). Causes of non- random mating are: inbreeding per se (mating with an individual with whom you share more genes than random), assortative mating (e.g., choosing a mate based on some phenotypic attribute), geographic proximity. - The single-locus result of non-random mating is to cause the population to deviate from Hardy-Weinberg equilibrium. - If individuals that share more genes than expected are more likely to mate, the result is an excess of homozygotes over the H-W expectation. Consanguinous mating, positive assortative mating, geographic isolation produce this result - If individuals that share more genes than expected are less likely to mate than expected, excess of heterozygotes Self-incompatibility mechanisms in plants, incest taboos in humans produce this result - Define f as the probability that two gene copies are Identical by Descent at some time in the recent past (we are not restricting the status of I by D to the previous generation as I did previously). An interesting way to think of f is as the "Probability of Homozygosity due to Special Circumstances" (PHSC, pronounced phonetically). that in the lecture in which I introduced the notion of identity by descent (which I
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This note was uploaded on 03/01/2010 for the course PCB 4683 taught by Professor Williams,j during the Spring '08 term at University of Central Florida.

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Lecture 7 - Non-random mating - 1 The Neutral Theory, Part...

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