Problems in Population Genetics
Frequency:
the number of times that a value appears in a set. In the set {1,3,3,4,2,5}, the
frequency of the value “3” is 2 and the frequency of the value “5” is 1.
Relative Frequency
: the frequency expressed as a proportion of the total number of values in
the set. Thus, in the example above, the frequency of “3” is 2/6 or 0.333…
In population genetics, we talk about relative frequency, but shorten the term to “frequency”.
Frequency and probability are related. If we know that ¼ of the alleles at a particular gene locus
in a population are “ob” (as opposed to wild type, “ob+”), and we randomly select 1 egg from the
population, then the
probability
that the egg will have the “ob” allele is 0.25. If we then replace
that egg and sample 100 times, at what frequency would we get an “ob” egg? That frequency
would also be around 0.25.
Problem 1
.In a population of voles, fur color is determined by a single locus. The population is
very large, and immigration, emigration, and selection are negligible. The genotypes AA and Aa
have the BROWN fur phenotype. The genotype aa has the WHITE fur phenotype. In the
population, 50% of the alleles at this locus are “A” and 50% of the alleles are “a”.
a.
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 Winter '10
 hunter
 Genetics

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