All are true about hemophilia, except
**Core Concept**
Hemophilia is a group of hereditary genetic disorders caused by deficiencies in coagulation factors, leading to impaired blood clotting and increased risk of bleeding. The two main types of hemophilia are Hemophilia A, caused by a deficiency in clotting factor VIII, and Hemophilia B, caused by a deficiency in clotting factor IX.
**Why the Correct Answer is Right**
Hemophilia A and B are both X-linked recessive disorders, meaning the genes responsible for these conditions are located on the X chromosome. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). As a result, males are more frequently affected by hemophilia than females, as they have only one X chromosome to carry the defective gene. Females can be carriers of hemophilia, but they typically do not exhibit symptoms due to the presence of a second, healthy X chromosome.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because hemophilia is not caused by a deficiency in clotting factor XI, but rather by deficiencies in clotting factors VIII and IX.
**Option B:** This option is incorrect because hemophilia is not transmitted in an autosomal dominant pattern, but rather in an X-linked recessive pattern.
**Clinical Pearl / High-Yield Fact**
It's essential to note that hemophilia A and B can be diagnosed through genetic testing, and both conditions can be managed with clotting factor replacement therapy. Additionally, females who are carriers of hemophilia can have a 50% chance of passing the defective gene to their offspring, making genetic counseling an important aspect of managing these conditions.
**Correct Answer:** D.