Question

It has been hypothesized that people who are heterozygous for the allele that causes the deadly genetic condition cystic fibrosis (which, among other symptoms, reduces fertility) are more resistant to the deadly disease tuberculosis.

Q9. 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.

Answer 1