You are studying a lab population of guppies of approximately 150 individuals. Y

Question

You are studying a lab population of guppies of approximately 150 individuals. You have collected genotype data for a "neutral" locus and calculate heterozygosity (H) to be 0.33 [Section 7.2 "Genetic Drift" and Box 7.4 on page 251]. Predict the heterozygosity following 2 generations of genetic drift. A colleague informs you that male guppies aggressively compete with each other for access to females, and this behavior results in a 5:1 female to male breeding ratio. Calculate the effective population size (N_-e) under this circumstance and use it to predict the loss of heterozygosity after 2 generations of genetic drift. Why does the unequal sex ratio alter your prediction from part a?

Explanation / Answer

b) In case of unequal no. of mating males and females , the effective population size will be

4Nm N f /( Nm + N f ) Nm = Number of breeding males, Nf = Number of breeding females

=4(1) (5) / (1 + 5) = 33.3. As the exact number of breeding male and famale is not known, so effective population size is estimated based on the ratio only. In such population where unequal breeding ratio persists heterozygosity will increase after two generations of genetic drift.

a) Following two generations of genetic drift heterozygosity decreases in small population. So the value will be less than .33. Heterozygosity after two generations of geneic drift can be calculated by the formula

H t = H0 (1- 1/2N) t

C) Females increase heterozygosity. More the number of females than males for mating lesser will be chances of inbreeding.

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