Question

use the pedigree on the right to determine which of the following are possible genotypes for irene.
x^{h}y
x^{h}x^{h}
x^{h}y
x^{h}x^{h}
what chance does irene have of being a carrier?
express your answer in a percentage.
%

Explanation:

Step1: Analyze the sex of Irene

Irene is female. So her genotype cannot be \(X^{H}Y\) or \(X^{h}Y\) (these are male genotypes).

Step2: Analyze the inheritance from parents

Ann (mother) is \(X^{H}X^{h}\) (since she is a carrier as half - shaded in the pedigree) and John (father) is \(X^{H}Y\). The possible genotypes for their female offspring (Irene) are obtained from the cross \(X^{H}Y\times X^{H}X^{h}\). Using the Punnett square:

Gametes of father	Gametes of mother
\(X^{H}\)	\(X^{H}X^{H}\)	\(X^{H}X^{h}\)

So the possible genotypes for Irene are \(X^{H}X^{H}\) and \(X^{H}X^{h}\).

Step3: Calculate the probability of being a carrier

From the Punnett square, out of 2 possible female genotypes (\(X^{H}X^{H}\) and \(X^{H}X^{h}\)), 1 is the carrier genotype (\(X^{H}X^{h}\)). The probability \(P=\frac{1}{2}=0.5 = 50\%\)

Answer:

Possible genotypes: \(X^{H}X^{h}\), \(X^{H}X^{H}\). Chance of being a carrier: \(50\%\)