Use the following information to answer the next two questions.
Cystic fibrosis is a recessive Mendelian trait in the human population. A symptom of cystic
fibrosis is the production of large amounts of mucin protein. New studies indicate that
although the cystic fibrosis condition is present at birth, increased mucin production is
preceded by an infection with the bacterium Pseudomonas aeruginosa. Individuals who are
not affected by cystic fibrosis produce a natural antibiotic, defensin, that kills the
Pseudomonas aeruginosa and eliminates the stimulus for increased mucin production.
Defensin is destroyed by a high chloride content in the tissues of individuals with cystic
fibrosis as a result of faulty chloride-channel proteins.
-from Sternberg, 1997
31. The allele that causes cystic fibrosis most likely results in a faulty amino acid
sequence for the
A. channel proteins
B. mucin molecules
C. defensin molecules
D. Pseudomonas bacteria
