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 2-8 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 4 generations of queen Victoria’s family. On of queen Victoria’s son, 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. 2 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 2 sons with a man that does not have hemophilia. Both sons have hemophilia.

Which statement best explains why none of Queen Victoria’s daughters had hemophilia?

Males with hemophilia must inherit the gene from their father since it is a recessive trait.
Hemophilia is a dominant trait that can only be passed down by the father.
Hemophilia can only be inherited by male offspring.
Females with hemophilia must inherit the gene from both parents to be affected.