Question

what are the odds that two carriers for cystic fibrosis, an autosomal recessive disorder, would have an offspring with the cystic fibrosis disorder? 0/4 1/4 1/2 3/4

Explanation:

Step1: Determine the genotypes of the parents

Let \(C\) represent the normal allele and \(c\) represent the allele for cystic fibrosis. Since both parents are carriers, their genotypes are \(Cc\).

Step2: Set up the Punnett square

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

	\(C\)	\(c\)
\(c\)	\(Cc\)	\(cc\)

Step3: Calculate the probability of having an affected offspring

The genotype \(cc\) is affected. Out of 4 possible genotypes (\(CC\), \(Cc\), \(Cc\), \(cc\)), only 1 is \(cc\). So the probability is \(\frac{1}{4}\).

Answer:

\(\frac{1}{4}\) (corresponding to the second option in the given choices)