One moth population carries three alleles at a genetic locus: X1, X2and X3. X1is dominant to X2and X3; X1produces red antennae. X2is co-dominant to X3; X2X2produces yellow antennae, X3X3produces white antennae, and X2X3produces light yellow antennae. The phenotypes in a population are as follows: 0.04 white; 0.16 light yellow; 0.16 yellow; 0.64 red. Assuming that this population is in Hardy-Weinberg equilibrium, what is the frequency of the X3allele in this population

The correct answer is - 0.20

Explanation:

According to Hardy Weinberg equation under specific conditions the frequencies of the allele in the gene in a given population remain constant. Thus according to this frequencies of allele and genotype will remain the same through the generation unless there will be no evolutionary influence.

It helps us to predict the genotype frequencies in a large population.  If there are two alleles having allelic frequencies p and q and we know equation of probability and frequencies add to 1

p2+2pq+q2=1

The X3X3 genome produces white antennae. Now Phenotypic frequency of the white antennae is 0.16 or 0.04 in the whole population. Hence the frequency of X3 should be a square root of 0.04 i.e, 0.20.

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