-Hemophilia is a genetic disease that has plagued the royal houses of Europe since the time of Queen Victoria, who was a carrier. Her granddaughter, Alexandra, married Nicholas II, the last czar of imperial Russia. Alexandra was a carrier for hemophilia, but Nicholas was normal. Their son, Alexis, was afflicted with the disease. Based on this scenario, it is most likely that
A) all four sisters were carriers of the hemophilia gene.
B) at least one of the sisters had hemophilia.
C) each of the sisters had a 50% chance of being a carrier of the gene.
D) Alexis inherited the hemophilia gene from Nicholas II.
E) none of the four sisters carried the hemophilia gene.

Question

-Hemophilia is a genetic disease that has plagued the royal houses of Europe since the time of Queen Victoria, who was a carrier. Her granddaughter, Alexandra, married Nicholas II, the last czar of imperial Russia. Alexandra was a carrier for hemophilia, but Nicholas was normal. Their son, Alexis, was afflicted with the disease. Based on this scenario, it is most likely that
A) all four sisters were carriers of the hemophilia gene. 
B) at least one of the sisters had hemophilia. 
C) each of the sisters had a 50% chance of being a carrier of the gene. 
D) Alexis inherited the hemophilia gene from Nicholas II. 
E) none of the four sisters carried the hemophilia gene.

Quizplus · Accepted Answer

Hemophilia is a sex-linked recessive trait, which means that females (XX) can be carriers of the disease without having the disease themselves, while males (XY) can only be affected if they inherit the defective gene from their mother. Since Alexandra was a carrier, each of her daughters had a 50% chance of inheriting the carrier status.

-Hemophilia Is a Genetic Disease That Has Plagued the Royal