Question

two normal parents that carry the gene for cystic fibrosis have a child. what are the chances their child will have cf? (hint: cf is an autosomal recessive disorder.) 75% 0% 50% 100% 25%

Explanation:

Step1: Determine the parents' genotypes

Since CF is autosomal recessive and parents are carriers (normal but carry the gene), their genotypes are \(Aa\) (where \(A\) is the normal allele and \(a\) is the CF - causing allele).

Step2: Create a Punnett square

The possible gametes from each parent are \(A\) and \(a\). The Punnett square is:

	\(A\)	\(a\)
\(a\)	\(Aa\)	\(aa\)

Step3: Analyze the genotypes

The genotypes of the offspring are \(AA:Aa : aa=1:2:1\). The \(aa\) genotype represents the child with CF.

Answer:

25%