Below are the numbers of individuals of migratory green warblers and the frequencies of three genotypes at a single locus for this species. F refers to the allele for faster migration and S to the allele for slower migration.
| FF | FS | SS | Total | |
|---|---|---|---|---|
| Number of individuals | 35 | 20 | 10 | 65 |
| Genotype frequencies | 0.54 | 0.30 | 0.16 | 1 |
What are the allele frequencies of F and S? (round off to 2 decimal places)
GATE Life Sciences - 2026,
Answer: A
The allele frequencies are F = 0.69 and S = 0.31.
Count alleles: each of the 65 birds carries two, 130 in all. FF birds carry two F alleles each and FS birds one.
\[ \begin{aligned} p(F) &= \frac{2(35) + 20}{130} = \frac{90}{130} \approx 0.69 \\ q(S) &= \frac{2(10) + 20}{130} = \frac{40}{130} \approx 0.31 \end{aligned} \]
The same result follows from the genotype frequencies: \(p = 0.54 + \frac{0.30}{2} = 0.69\), and \(p + q = 1\) gives \(q = 0.31\).
The option with F = 0.31 and S = 0.69 swaps the two alleles. The 0.59 and 0.50 options do not come from any correct count; 0.50 would require equal numbers of FF and SS birds.
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