Question

If the cystic fibrosis allele protects against tuberculosis the same way the sickle-cell allele protects against malaria, then which of the following should be true of a comparison between regions with and without tuberculosis? Cystic fibrosis deaths should be more common in regions with tuberculosis. Cystic fibrosis deaths should be less common in regions with tuberculosis. Cystic fibrosis deaths should be equally common in both types of regions. Regional differerces in the cystic fibrosis death rate should be purely random and unpredictable.

Answer 1

Cystic fibrosis deaths should be less common in regions with tuberculosis if the cystic fibrosis allele confers a selective advantage, similar to how sickle-cell allele carriers have resistance against malaria.

Step-by-step explanation:

If the cystic fibrosis allele indeed provides a heterozygote advantage by conferring protection against tuberculosis in a similar manner to how the sickle-cell allele provides resistance against malaria, we would expect that cystic fibrosis deaths should be less common in regions with tuberculosis.

This is because carriers of the cystic fibrosis allele who have one normal and one mutant gene may have a selective advantage, leading to a higher frequency of the allele in tuberculosis-endemic areas. On the other hand, individuals with two copies of the cystic fibrosis allele would suffer from the disease itself, which can be fatal without medical intervention.

Thus, the pattern of deaths due to cystic fibrosis would not be purely random and unpredictable, nor would it be equally common in both types of regions, since the selective pressure exerted by tuberculosis would influence the prevalence of the allele in the population.