Question

Which of the following most appropriately describes hemophilia?
A. Dominant gene disorder
B. Recessive gene disorder
C. X-linked gene disorder
D. Chromosomal disorder

Answer 1

Hint: Haemophilia is a genetic disorder in which the blood clotting factor or protein is defective due to which the exposed blood of the hemophilic individuals fails to coagulate. Moreover, haemophilia is of two types, haemophilia A and haemophilia B, where haemophilia A is a more severe form.

Complete answer: Haemophilia is an X-linked recessive genetic disorder. Its transmission occurs from a normal heterozygous carrier female to the male progeny. The blood of the hemophilic individuals cannot clot if they are exposed to any injury. This is because of the defective form of the blood proteins.
The possibility of females being hemophilic is very rare. Moreover, haemophilic females die before birth.
In Haemophilia A, the person cannot synthesize the normal blood protein known as antihemophilic globulin or AHG. AHG is required for normal blood clotting. Hence, even a small cut on the body causes bleeding for very long periods. The gene for hemophilia A is located on the X chromosome and it is recessive. This gene remains latent in the carrier females. In Hemophilia B the plasma thromboplastin is absent. It is also known as the Christmas disease. The inheritance of hemophilia B is similar to hemophilia A. Thus, based on the above information we can conclude that Hemophilia is an X-linked gene disorder.
Hence, the correct answer is option (C).

Note: Haemophilia is observed in the Royal family of the Queen of England. The family pedigree of Queen Victoria shows a number of descendants having haemophilia. This is because Queen Victoria was a carrier for the gene of haemophilia. Due to this reason, several of her later generations were either carriers of haemophilia.