GRE Subject Test: Biology : Understanding Genetic Drift

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Understanding Genetic Drift

Genetic drift is a phenomenon by which __________ in a population change.

Possible Answers:

mutation frequencies

allele frequencies 

random mating

natural selection

Correct answer:

allele frequencies 

Explanation:

Genetic drift specifically refers to the change of allele frequencies because of random sampling of gametes. Essentially, this induces genetic bias for particular alleles and can lead to speciation events simply by the chance event of certain gametes producing offspring rather than others.

Changes in mutation frequencies, random mating, and natural selection may lead to changes in allele frequencies, but they are not necessarily the cause of genetic drift. 

Example Question #2 : Understanding Genetic Drift

Which of the following factors plays the biggest role in the impact of genetic drift on a population?

Possible Answers:

Random chance

Immigration of animals

Natural selection

Mating preferences

Correct answer:

Random chance

Explanation:

Genetic drift occurs when a gene's frequency is changed in a population due to pure chance. Consider a rock rolling down a hill and crushing all flowers that have white petals. The population will now have only red petals because the white ones were destroyed. Were the red petal flowers more suited to their environment? No, it just so happened that all of the white were removed from the gene pool. This shows that evolution can occur due to random chance as well as natural selection, and both forces can have an impact on a population.

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