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Given above model for heterosis A. Assume 2 loci, each with allele frequency .5,

ID: 181122 • Letter: G

Question

Given above model for heterosis

A. Assume 2 loci, each with allele frequency .5, the population is subdivided, and allowed to mate at random within each. But due to limited effective population size, each population becomes 100% inbred.

What are the expected genotypic frequencies of each locus in each population given the initial frequencies and level of inbreeding? Because each locus drifts independently there are 4 possible combinations of genotypic frequencies between lines.

For each of those 4 possible parent line combinations, cross the populations. What are the expected frequencies of genotypes among the F1 offspring.

What are the expected mean phenotypes of the parents and the F1given the Dominance model above .

From these examples, which combinations gave an F1 greater than the mean of the parents and which gave an F1 greater than either parent?

Dominance model AA-40 BB-20 Aa-40 Bb=0 aa=0 bb=0 aaBB AAbb AaBb 200 Bbb 00 Dm 440 aa Aa

Explanation / Answer

100% inbred means, Inbreeding coefficient =1

'AA' genotype = 40

‘Aa’ genotype = 40

Allele frequency of ‘A’ = 40+1/2*40 = 60 = 0.6

Allele frequency of 'a' = 1/2*40 = 20 = 0.2

'BB' genotype = 20

Allele frequency of 'B' = 20 or 0.2

Allele frequency of 'b' = 0

Four possible genotypes frequencies can be: AABB, AABb/bb, AaBB, AaBb/bb

In F1 generation, the expected mean phenotypes of the offsprings AaBb will be 0.2.

The expected mean phenotypes of parents will be 0.3.

** Hope it helps.

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