Hemophilia is a rare bleeding disease that is carried on the X-chromosome. More than 400,000 people worldwide live with this disease, 20,000 of those within the United States. It is commonly called the "royal disease" because Queen Victoria was known to be a carrier of the disease and passed the gene to other members of the royal family.

If a healthy individual who does not have hemophilia gets a small cut on their arm, it takes two to eight minutes on average for clotting to occur and for the bleeding to stop. People suffering from hemophilia lack an essential blood-clotting protein in their blood plasma. If they get cut, it can take 30 minutes to 22 hours for the bleeding to stop. Excessive bleeding is a constant danger to individuals with hemophilia.

Figure 1 shows the pedigree of hemophilia in four generations of Queen Victoria's family.

Pedigree showing four generations of Queen Victoria's family. One of Queen Victoria's sons, Leopold, has hemophilia. One of Queen Victoria's daughters, Alice, is a carrier of the gene for hemophilia. Alice has children with a man that does not have hemophilia. Two of Alice's daughters, Alexandra and Irene, carry the gene for hemophilia, and her son has hemophilia. Alexandra has a son, Alexis, with a man that does not have hemophilia. Alexis has hemophilia. Irene has two sons with a man that does not have hemophilia. Both sons have hemophilia.

Using the pedigree, which statement is true about Leopold's family?
a- If Leopold had a second male child, that son would have inherited hemophilia.
b- Leopold's daughter, Alice, is homozygous recessive for the hemophilia trait.
c- Leopold's son can't have a biological female child with hemophilia.
d- The mother of Leopold's children must be a carrier of hemophilia because the daughter is a carrier.