Biology 11th Edition by Gerald Audesirk,Teresa Audesirk,Bruce Byers

Exercise 14

The defective CFTR alleles that cause cystic fibrosis vary tremendously in their severity. Some produce completely nonfunctional proteins, while others produce proteins that can transport chloride, just not as efficiently as the normal proteins do. Many people with cystic fibrosis are heterozygotes: They have two different defective CFTR alleles. How might the severity of cystic fibrosis symptoms depend on the allele combination in heterozygotes? As good as the better-functioning allele? As bad as the worsefunctioning one? Somewhere in between? Why?