MCAT Biology : Other Evolution Principles

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #1 : Other Evolution Principles

Inbreeding reduces the fitness of a population. This is the result of which increased genetic effect of inbreeding?

Possible Answers:

Expression of deleterious recessive traits

Rate of spontaneous mutation

Genetic diversity 

Levels of aggression

Correct answer:

Expression of deleterious recessive traits

Explanation:

Inbreeding increases the expression of recessive traits due to more heterozygous carriers mating with each other. As the same individuals mate, the chance of a homozygous recessive child increases. This is the same as estimating the likelihood of a single healthy child from two carrier parents (0.75) versus eight healthy children from two carrier parents (0.10).

Inbreeding decreases genetic diversity, rather than increasing it. The rate of spontaneous mutation is not impacted by this type of breeding. There is no reason to infer increased levels of aggression.

Example Question #1 : Other Evolution Principles

Which is not a necessary condition for the Hardy-Weinberg equation to be true?

Possible Answers:

No natural selection

No net migration of individuals into or out of the population

No mutations in the gene pool

Small population

Random mating

Correct answer:

Small population

Explanation:

For the Hardy-Weinberg equation to be true, the population in question must be very large. This ensures that coincidental occurrences do not drastically alter allelic frequencies.

Example Question #2 : Other Evolution Principles

In a population that is in Hardy-Weinberg equilibrium, the frequency of homozygous dominant individuals is 0.36. What is the percentage of homozygous recessive individuals in the population?

Possible Answers:

Correct answer:

Explanation:

The two equations pertaining to Hardy-Weinberg equilibrium are:

In this second equation, each term refers to the frequency of a given genotype.  is the homozygous dominant frequency,  is the heterozygous frequency, and  is the homozygous recessive frequency.

From the question, we know that:

We now know the dominant allele frequency. Using the other Hardy-Weinberg equation, we can find the recessive allele frequency:

Returning to our genotype frequency terms, we can use this recessive allele frequency to find the homozygous recessive frequency:

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