Question

in the pedigree that is shown, which represents irene’s allele combination?
options: ( x^hx^h ), ( x^h x^h ), ( x^h x^h ), ( x^h y )

Explanation:

Irene is a female (circle in pedigree), so her genotype is XX. Her parents are \(X^H Y\) (father) and \(X^H X^h\) (mother). From father, she gets \(X^H\); from mother, possible \(X^H\) or \(X^h\). But Fred (affected, male) has \(X^h Y\) (since he's affected, recessive X - linked? Wait, Marie is \(X^H X^h\) (carrier, half - shaded), Charles is \(X^H Y\), their son is affected (so \(X^h Y\)). Parents of Fred/Jack/Irene: father \(X^H Y\), mother \(X^H X^h\). For Irene (female, not shaded, so not affected, so she must have \(X^H X^H\) or \(X^H X^h\)? Wait, no—wait the options: \(X^h X^h\) (affected female, would be shaded), \(X^H X^h\) (carrier, half - shaded), \(X^H X^H\) (unaffected, not shaded), \(X^h Y\) (male). Irene is a circle (female) and unshaded, so she can't be \(X^h Y\) (male). Her father is \(X^H Y\) (gives \(X^H\)), mother is \(X^H X^h\) (can give \(X^H\) or \(X^h\)). But since she's unshaded (not a carrier or affected), she must be \(X^H X^H\)? Wait no, wait the mother is \(X^H X^h\) (half - shaded, carrier), father \(X^H Y\). So for daughters: possible genotypes from father (\(X^H\)) and mother (\(X^H\) or \(X^h\)): \(X^H X^H\) (unaffected, not shaded) or \(X^H X^h\) (carrier, half - shaded). Irene is unshaded, so \(X^H X^H\)? Wait the options: one of the options is \(X^H X^H\) (assuming the third option is \(X^H X^H\)). Wait the options are: \(X^h X^h\), \(X^H X^h\), \(X^H X^H\), \(X^h Y\). Irene is female (XX), unshaded, so she's \(X^H X^H\) (since if she were \(X^H X^h\), she'd be half - shaded like her mother, but she's unshaded). So the correct allele combination is \(X^H X^H\).

Answer:

\(X^H X^H\) (assuming the third option is labeled as, for example, C. \(X^H X^H\), then the answer would be C. \(X^H X^H\))