AP Biology Free Response Question

Topics: Population genetics, Allele frequency, Evolution Pages: 3 (1158 words) Published: March 10, 2015

December 3,

Respond to the following.
1. Distinguish genetic drift from gene flow in terms of how they occur and their implications for future genetic variation in a population.
Genetic drift, defined as the process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next, can increase or decrease variability within particularly small populations. Certain genotype/phenotype frequencies, for example, may be reduced or completely eliminated through chance events. Examples of genetic drift might include the founder effect, which consists of a select amount of individuals is separated from a larger population and eventually establishes a gene pool different from that of the source population, or the bottleneck effect, in which a severe drop in population size can leave some alleles overrepresented in survivors and others underrepresented. In contrast, gene flow is the transfer of alleles into or out of a population due to the movement of fertile individuals on their gametes. Unlike the random favoring of traits that comes about through genetic drift, gene flow can transfer alleles that improve the ability of populations to adapt to local conditions, ultimately becoming a mechanism of natural selection. Adhering to the definition of natural selection, individuals with beneficial traits survive and reproduce more efficiently- thus increasing the flow of favorable genes throughout a population. In fact, it has become an increasingly important agent of evolutionary change in human populations. Individuals moving into a population can bring new alleles into the gene pool whereas other alleles can be completely eliminated as other individuals leave the population. Genetic variation within future populations, thusly, increases drastically, due to the introduction of new traits and alleles. Although genetic drift and gene flow differ in the ways that they change allele...
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