MCAT Biology : Other Evolution Principles
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Example Question #1 : Other Evolution Principles
Inbreeding reduces the fitness of a population. This is the result of which increased genetic effect of inbreeding?
Rate of spontaneous mutation
Expression of deleterious recessive traits
Genetic diversity
Levels of aggression
Expression of deleterious recessive traits
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 : Understanding Hardy Weinberg Equilibrium
Which is not a necessary condition for the Hardy-Weinberg equation to be true?
Random mating
No mutations in the gene pool
No net migration of individuals into or out of the population
No natural selection
Small population
Small population
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 #4 : Evolution And Mutations
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?
The two equations pertaining to Hardy-Weinberg equilibrium are:
In this second equation, each term refers to the frequency of a given genotype. 
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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