Question

Cystic fibrosis is an autosomal recessive disorder caused by a single gene in humans. If individual #1 who is homozygous recessive at this gene mates with individual #2 who is homozygous dominant at this gene, then what is the chance that their child will have the disorder?

0%
50%
100%
25%

Answer 1

Individuals with one homozygous recessive parent (ff) and one homozygous dominant parent (FF) will have a 0% chance of having cystic fibrosis, as they will all be carriers (Ff) without exhibiting the disease.

Step-by-step explanation:

Cystic fibrosis is an autosomal recessive disorder caused by mutations in a single gene on an autosome. When a person who is homozygous recessive (ff) for cystic fibrosis mates with someone who is homozygous dominant (FF), all of their children will receive one mutant allele and one normal allele, making them carriers (Ff) but not affected by the disease.

Therefore, if individual #1 who is homozygous recessive at the cystic fibrosis gene (ff) mates with individual #2 who is homozygous dominant (FF), their children will have a 0% chance of having cystic fibrosis because they will all inherit one dominant and one recessive allele (Ff), being carriers but not manifesting the disease.