What is the mode of genetic transmission for hemophilia B?

Hemophilia B is a genetic disorder characterized by a deficiency in clotting factor IX, which is essential for proper blood coagulation. The mode of transmission for this disorder is X-linked recessive.

In X-linked recessive inheritance, the gene causing the condition is located on the X chromosome. Males (XY) have only one X chromosome, so if they inherit an X chromosome that carries the hemophilia B gene mutation, they will express the disorder because they lack a second X chromosome that could provide a normal copy of the gene. Females (XX), on the other hand, would need to inherit two copies of the mutated gene (one from each parent) to express the disorder, as they have a second X chromosome that can potentially have the normal gene. As a result, hemophilia B is primarily observed in males, while females who carry one mutated gene typically do not show symptoms but can pass the trait to their offspring.

This understanding highlights why hemophilia B follows the X-linked recessive pattern of genetic transmission, making the answer appropriate.