Question

franks sister is known to carry an allele for a single - gene recessive genetic disorder that is fatal in very early life. franks mother was tested for the allele and found not to carry it. what are the odds that frank is a carrier for the allele? correct answer(s) 1/1 1/8 1/2 1/4 incorrect answer(s)

Explanation:

Step1: Determine the father's genotype

Since Frank's sister is a carrier (\(Aa\)) and the mother is \(AA\) (not a carrier), the father must be \(Aa\) (because the sister got one \(a\) allele from the father).

Step2: Calculate the probability of Frank getting the allele from the father

When the father (\(Aa\)) and mother (\(AA\)) have a child, the possible genotypes of the child are \(AA\) or \(Aa\). The probability of getting \(Aa\) (carrier) from the father - mother cross (\(Aa\times AA\)) is \(\frac{1}{2}\).

Answer:

\(\frac{1}{2}\)