The allele for the hair pattern widow's peak is dominant. In a population of 1000 individuals, 510 show the dominant phenotype. How many individuals would you expect of each of the possible 3 genotypes for this trait? How do you answer this?

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The allele for the hair pattern widow's peak is dominant. In a population of 1000 individuals, 510 show the dominant phenotype. How many individuals would you expect of each of the possible 3 genotypes for this trait? How do you answer this?

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Answer 1 · 2016-09-29T05:11:59

For the homozygous dominant genotype there will be $90$ $90$ individuals. For the heterozygous genotype there will be $420$ $420$ individuals and for the homozygous recessive genotype there will be $490$ $490$ individuals.

Explanation:

You answer this by using Hardy-Weinberg Equation.

From the $1000$ $1000$ individuals, we know that $510$ $510$ show dominant phenotype but we don't know how many of those individuals are homozygous dominant or heterozygous because both show dominant trait.

But we can infer that the remaining $490$ $490$ individuals show recessive trait and therefore have homozygous recessive genotype.

$\frac{490}{1000} = 0.49 = q^{2}$ $490/1000 = 0.49 = q^2$

$0.7 = q$ $0.7 = q$

$p + q = 1$ $p + q = 1$

$p = 1 - q$ $p = 1 - q$

$p = 0.3$ $p = 0.3$

Then

$p^{2} = 0.09$ $p^2 = 0.09$

$q^{2} = 0.49$ $q^2 = 0.49$

$2 p q = 2 (0.7) (0.3) = 0.42$ $2pq = 2(0.7)(0.3) = 0.42$

Double Check:

$p^{2} + 2 p q + q^{2} = 1$ $p^2 + 2pq + q^2 = 1$

$0.09 + 0.42 + 0.49 = 1$ $0.09 + 0.42 + 0.49 = 1$

You thus have

$0.09 (1000) = 90 \to$ $0.09(1000) = 90 ->$ with homozygous dominant genotype

$0.42 (1000) = 420 \to$ $0.42(1000) = 420 ->$ with heterozygous genotype

$0.49 (1000) = 490 \to$ $0.49(1000) = 490 ->$ with homozygous recessive genotype

Double Check:

$90 + 420 + 490 = 1000 individuals$ $90 + 420 + 490 = "1000 individuals"$

$90 + 420 = 510 individuals \to$ $90 + 420 = "510 individuals " ->$ with dominant phenotype

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The allele for the hair pattern widow's peak is dominant. In a population of 1000 individuals, 510 show the dominant phenotype. How many individuals would you expect of each of the possible 3 genotypes for this trait? How do you answer this?

1 Answer

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