Which statement correctly describes the hemophilia A trait?

Which statement correctly describes the hemophilia A trait?

• A. It is an X-linked recessive trait found primarily in females.
• B. It is an X-linked dominant trait found primarily in females.
• C. It is an X-linked recessive trait found primarily in males.
• D. It is an X-linked dominant trait found primarily in males.

Answer: (C)

Hemophilia A is characterized as an X-linked recessive trait that predominantly affects males. This means that the gene responsible for hemophilia A is located on the X chromosome. Males have one X and one Y chromosome (XY); if the X chromosome they inherit carries the hemophilia A gene mutation, they will express the trait since they do not have a second X chromosome that could potentially carry a normal allele to mask the mutation. Females, on the other hand, have two X chromosomes (XX). Thus, for a female to express hemophilia A, she would need to inherit the affected X chromosome from both parents. In most cases, females with one affected X chromosome are carriers of the hemophilia A trait but do not show symptoms due to the presence of a normal allele on the other X chromosome. This distinction is key in understanding the gender prevalence seen in hemophilia A cases, as it is primarily males who exhibit the condition due to their single X chromosome inheritance pattern.

Hemophilia A is characterized as an X-linked recessive trait that predominantly affects males. This means that the gene responsible for hemophilia A is located on the X chromosome. Males have one X and one Y chromosome (XY); if the X chromosome they inherit carries the hemophilia A gene mutation, they will express the trait since they do not have a second X chromosome that could potentially carry a normal allele to mask the mutation.

Females, on the other hand, have two X chromosomes (XX). Thus, for a female to express hemophilia A, she would need to inherit the affected X chromosome from both parents. In most cases, females with one affected X chromosome are carriers of the hemophilia A trait but do not show symptoms due to the presence of a normal allele on the other X chromosome.

This distinction is key in understanding the gender prevalence seen in hemophilia A cases, as it is primarily males who exhibit the condition due to their single X chromosome inheritance pattern.