A mouse mutation with incomplete dominance (t = tailless) causes short tails in
ID: 64600 • Letter: A
Question
A mouse mutation with incomplete dominance (t = tailless) causes short tails in heterozygotes (t+/t). The same mutation acts as a recessive lethal that causes homozygotes (t/t) to die in utero. In a population consisting of 150 mice, 60 are t+/t+ and 90 are heterozygotes. What are the allele frequencies in this population? Given that there is random mating among mice, no migration, and no mutation, and ignoring the effects of random genetic drift, what are the expected numbers of the different genotypes in this next generation if 200 offspring are born?
Explanation / Answer
f(t+t+) = 60/150=0.4
f(t+t) = 90/150= 0.6
Current generation: f(t+) = (2 f(t+t+) + f(t+t)) / 2
= (2 * 0.4+ 0.6) / 2
= 0.7
f(t) = 1 - f(t+) = 0.3
In the next generation, total individual= 200
Genotype t+t+ =0.4 * 200 = 80
Genotype t+t = 0.6 * 200 = 120
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