Question

A recessive gene located on the X chromosome is the cause of hemophilia in affected individuals. Males are more likely to have hemophilia than females because A. females have no copies of the X chromosome. B. hemophilia is associated with high testosterone levels. C. males have two copies of the X chromosome. D. males have only one copy of the X chromosome.

Answer 1

The right answer is D. males have only one copy of the X chromosome.

Hemophilia is a rare hereditary bleeding disorder disease. The blood of hemophiliacs does not coagulate normally. Bleeding is not more important, but without treatment, they can be more frequent and last longer than normal. Hence the importance of good monitoring and good treatment.
The 2 types of hemophilia A and B are recessive and X-linked, but a third of hemophilia correspond to a de novo mutation. It is observed that a man who wears the X is always affected by the disease (because he has only one X chromosome in its genome) whereas the woman is only a carrier (she has two X chromosomes, so it can carry a safe X and a mutated X without being attempted by the disease but can transmit it to her descendants). This must be taken into account for genetic counseling.