Cystic fibrosis is caused by a recessive mutant allele cf Tw

Cystic fibrosis is caused by a recessive mutant allele (cf). Two normal parents produce a child with cystic fibrosis. What are the genotypes of the parents? a. CF/cf and CFICF b. CF/cf and cf/cf c. Both are CF/cf d. CF/CF and cf/cf What is the probability of this family having four children, 1 with cystic fibrosis, and 3 without cystic fibrosis? a. 0.14 b. 0.25 c. 0.047 d. 0.42

Solution

19. Answer is option C. Both are CF/cf

It is caused by the presence of mutations in both copies of the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Those with a single working copy are carriers and otherwise mostly normal.

20.answer is option B. 0.25

Out of the 4 children, 0.25 will be healthy, 0.50 will be carriers and 0.25 will have disease.