Question

A person who is heterozygous for the cystic fibrosis allele moves to a small, isolated community where no one previously carried the allele. If the cystic fibrosis allele protects against tuberculosis the same way the sickle-cell allele protects against malaria, what should happen to the frequency of the cystic fibrosis allele in the community over time, and why?

The cystic fibrosis allele should disappear from the population, because a single individual with the allele is not enough for it to proliferate.

The cystic fibrosis allele should increase to a relatively high frequency, because heterozygotes with the allele will be more likely to survive than others.

The cystic fibrosis allele should become fixed in the population, due to genetic drift.

The cystic fibrosis allele should either disappear or increase in frequency, depending on chance as well as on tuberculosis prevalence and death rate.

2)

You visit a huge city with millions of people. If you were to start sampling the cystic fibrosis allele from one generation to the next, what should happen to its frequency over the next few generations, and why?

The allele frequency should change a lot from one generation to the next due to random genetic drift.

The allele frequency should not change much from one generation to the next because the population is large.

The allele frequency should steadily increase due to natural selection.

The allele frequency should steadily decrease due to natural selection.