Question

The family pedigree of Queen Victoria shows a number of hemophilic Descendents as-
A. She herself was hemophilic.
B. Haemophilia is an autosomal recessive disorder.
C. Haemophilia is a sex-linked recessive disorder and Queen Victoria was a carrier.
D. Haemophilia is caused by contact and therefore it was seen in the royal family descendants.

Answer 1

Hint:Haemophilia is an inheritable genetic disorder. It impairs the body’s ability to form blood clots. It is required to stop excessive bleeding during cuts and injuries. The genes that code for clotting factors lie on the X-chromosome and are faulty or non-functional in disease.

Complete answer:Haemophilia is an inheritable genetic disorder linked with a lack of clotting factors produced by the body. The disease is caused by a mutation in the gene responsible for clotting factors production present on X-chromosome. Thus, it is an X-linked recessive disorder or sex-linked recessive disorder as an X-chromosome is a sex chromosome. A female should have both mutated X-chromosomes to be affected. On the other hand, a female having only one X-chromosome which has the mutation acts as a carrier. Queen Victoria too was a carrier.

Now, in males, there is only one X-chromosome and if it bears mutation then it is enough to cause the disease. Hence, males are more affected by hemophilia. The mutation transferred from Queen Victoria to the royal descendants in an X-linked recessive manner.
Hemophilia suffering person experiences excessive blood flow even from a minor cut that can lead to death. With the severe condition, the joints start bleeding and certainly lead to death.

Hence, option C is correct.

Note: The prevention from hemophilia is by removal of egg followed by fertilization and testing. Treatments include introducing artificial blood clotting factors. This can take place on a regular basis or at the time of bleeding episodes. Recombinant DNA technology has been used to manufacture artificial clotting factors.