MCAT Biology : Population Genetics and Hardy-Weinberg

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #31 : Population Genetics And Hardy Weinberg

A rare recessive mutation causes rabbits that are normally white to be pink. If one out of every 625 rabbits is pink, what percentage of the population is heterozygous?

Possible Answers:

Correct answer:

Explanation:

We can use the Hardy-Weinberg equilibrium formulas to calculate the allele frequencies.

\(\displaystyle p + q = 1\)

\(\displaystyle p^2+2pq+q^2=1\)

We know that the frequency of homozygous recessive (pink) rabbits is \(\displaystyle \frac{1}{625}\). This is equal to \(\displaystyle q^2\) in the Hardy-Weinberg calculation. We can use this information to solve for \(\displaystyle q\), the recessive allele frequency.

\(\displaystyle q^2=\frac{1}{625}\)

\(\displaystyle q = \sqrt{\frac{1}{625}} = 0.04\)

Now that we know the value of \(\displaystyle q\), we can solve for the value of \(\displaystyle p\).

\(\displaystyle p+q=1\)

\(\displaystyle p = 1- 0.04 = 0.96\)

The frequency of heterozygotes is equal to \(\displaystyle 2pq\) in the Hardy-Weinberg calculation. Now that we know the frequency of each allele, we can complete this calculation.

\(\displaystyle 2pq = 2(0.96)(0.04) = 0.077\)

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