One in 25 Caucasians Is a Carrier for the Defective

Multiple Choice

One in 25 Caucasians is a carrier for the defective CFTR gene,making it the most common genetic disease in this population.Why would the frequency of defects in CFTR be so common in this population,given the relationship between cholera and CFTR is similar in humans?

A) Carriers with one copy of the defective CFTR gene have decreased resistance to cholera compared to those with no defective copies.
B) Carriers with one copy of the defective CFTR gene have increased resistance to cholera compared to those with no defective copies.
C) Only carriers would be able to survive exposure to cholera.
D) These individuals were exposed to cholera, causing mutations in their CFTR gene that can then be passed on to their children.
E) Carriers will be more likely to have children who develop cystic fibrosis.