AP Biology : Population Genetics

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #21 : Understanding Genetic Drift, Bottleneck Effect, And Founder Effect

There was once a population on planet M311, called the Freg, who lived on a planet not unlike Earth. At the height of the Fregs technology and evolution, a collection of asteroids bombarded the planet and the devastation was so great that the planet was split in two, as was the Freg population. Much of the Freg population died, but many still survived on both pieces of M311.

The asteroid was an enormous catastrophe that drastically reduced the Freg population. As a result, their gene pool will be significantly smaller. What is this phenomenon called?

Possible Answers:

The Darwin Conundrum

The Bottleneck Effect

The Extinction Example

Radical Genetecism

The Dinosaur Hypothesis

Correct answer:

The Bottleneck Effect

Explanation:

The bottleneck effect is the correct answer here. The effect is defined as a sharp reduction in a populations size due to an environmental effect. In this scenario, the asteroids were the environmental effect and it caused the Freg population to decrease significantly. Also, none of the other answers are real theories.

Example Question #51 : Population Genetics

Which of the following is true of genetic drift?

Possible Answers:

Genetic drift helps reduce the frequency of harmful alleles in a population

None of these statements are true

The effects of genetic drift are negligible in smaller populations

Genetic drift involves the random change of allele frequencies in a population

Genetic drift only occurs in populations at Hardy-Weinberg equilibrium

Correct answer:

Genetic drift involves the random change of allele frequencies in a population

Explanation:

Genetic drift is a direct result of independent assortment. Since genes are not inherited by any organized mechanism, there are random fluctuations during which certain alleles experience an increase in frequency over others.

Genetic drift results in random changes in allele frequency; these changes are not a cause of genetic drift. In smaller populations and extreme cases, random changes can result in the loss of an allele entirely within the population. The results of genetic drift are more prominent in smaller populations due to their already reduced gene pool. Since genetic drift is random, both beneficial and harmful alleles can be promoted or eliminated.

Genetic drift cannot increase genetic diversity. The only way to increase genetic diversity is by the introduction of new traits and alleles. Genetic drift can reduce genetic diversity by eliminating alleles from a population, but is incapable of creating new traits. This can only be done through mutation.

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