Answer:
The options:
A. A hemophiliac mother and an unaffected father
B. A carrier mother and an unaffected father
C. A carrier mother and a hemophiliac father
D. An unaffected, non-carrier mother and a hemophiliac father
The CORRECT ANSWER IS C.
C. A carrier mother and a hemophiliac father
Explanation:
Hemophilia is known to be a recessive disorder, a woman would need to have two disease alleles (positioned on both X chromosome) for the disease to be expressed. Therefore, she would need to possess the disease allele from both parents (mother and father).
Hemophilia is an X-linked disorder, and it is hemizygous for male in terms of the hemophilia-related gene (with only a singular allele and express the phenotype linked with the allele). For the hemophilia allele to be inherited in an offspring, the male has to be hemophiliac.
Pairs of parents without a hemophiliac male would not have a hemophiliac daughter, excluding rare conditions (spontaneous mutations occuring in the germline or at growth and maturation of the embryo).
A homozygous woman for this condition (is hemophiliac) or heterozygous woman for the allele in consideration (is an unaffected carriers) could transfer a hemophilia allele to her offspring.
Pairs of parents that without a hemophiliac female or hemophiliac carrier would not yield a hemophiliac daughter (with the exclusion of rare spontaneous mutation situations).
Of the pairs above, a carrier mother and a hemophiliac father would most probably produce a hemophiliac daughter.
