Imagine that you are studying a very large population of moths that is isolated from gene flow. A single gene controls wing color. Half of the moths have white-spotted wings (genotype WW or Ww), and half of the moths have plain brown wings (ww). There are no new mutations, individuals mate randomly, and there is no natural selection on wing color. How will p, the frequency of the dominant allele, change over time?
A) p will increase; the dominant allele will eventually take over and become most common in the population.
B) p will neither increase nor decrease; it will remain more or less constant under the conditions described.
C) p will decrease because of genetic drift.
D) p will fluctuate rapidly and randomly because of genetic drift.

Question

Quizplus · Accepted Answer

In a population with no new mutations, random mating, no natural selection, and no gene flow, the frequency of the dominant allele is expected to remain stable over time. This is because both alleles have equal fitness and there is no selective advantage for either one. As a result, the frequency of the dominant allele is likely to remain around 0.5 (in this case, p=0.5) because it has an equal chance of being passed down to the next generation as the recessive allele. Since the population is isolated, genetic drift is not likely to cause significant changes in allele frequencies.

Imagine That You Are Studying a Very Large Population of Moths