Question

who has hemophilia in the pedigree that is shown?
john and ann
fred and luke
john, charles, jack, and irene
ann and marie

Explanation:

Hemophilia is an X - linked recessive disorder. Males with \(X^{h}Y\) genotype have hemophilia (since they have the recessive allele on the X - chromosome and Y has no corresponding allele). Looking at the pedigree: Fred has \(X^{h}Y\) and Luke has \(X^{h}Y\), so they have hemophilia. The other options: John and Ann (not in the given pedigree analysis), John, Charles, Jack, and Irene (Charles and Jack have \(X^{H}Y\) so no, Irene's genotype is unknown but not hemophilic here), Ann and Marie (Marie is a carrier \(X^{H}X^{h}\) not hemophilic).

Answer:

B. Fred and Luke