Semmelweis Medicine Biology Entrance Practice Exam

Hemophilia is a common sex-linked disease primarily caused by mutations in genes located on the X chromosome. It is a hereditary bleeding disorder where blood does not clot properly due to insufficient clotting factors. Since males have only one X chromosome (XY), a single mutated copy of the hemophilia gene inherited from their mother can lead to the disease. In contrast, females (with two X chromosomes) may be carriers without exhibiting symptoms unless both copies of the gene are mutated. This characteristic of being inherited through the X chromosome distinguishes hemophilia as a classic example of a sex-linked disorder.

In understanding sex-linked diseases, it's important to recognize the influence of genetic inheritance rules, particularly regarding how traits on the X chromosome manifest differently in males and females. Albinism and cystic fibrosis are not linked to the sex chromosomes; rather, they follow autosomal inheritance patterns. Muscular dystrophy, while it is a genetic condition associated with muscle degeneration, is primarily linked to specific types of muscular dystrophy, such as Duchenne muscular dystrophy, which is also due to mutations on the X chromosome. However, hemophilia directly exemplifies the male-specific inheritance pattern associated with sex-linked diseases, making it the most suitable answer in this context.