1Cystic fibrosis results from mutations in a single gene tha

1.Cystic fibrosis results from mutations in a single gene that lies on chromosome 7. Only homozygous mutant (ff) individuals are sick; homozygous wild-type (FF) and heterozygous (Ff) individuals are healthy. A healthy married couple has one child with cystic fibrosis and the wife is pregnant with a second child.

What is the genotype of the mother and father?

a) FF

b) Ff

c) ff

2. In the above case of cystic fibrosis, what is the chance that the second child will have cystic fibrosis?

a) 25%

b) 50%

c) 100%

Solution

1. the genotype of the mother and father is Ff. here both parent are heterozygous for the responsible allele. the ratio of the generation from these patient are- normal 25%, carrier50%, affected 25%.

2. here only 25% chance of second child being affected by cystic fibrosis.