Question

Why is haemophilia more common in males?

Answer 1

Hemophilia is a bleeding disorder caused by a genetic defect due to which blood doesn't clot correctly. Due to hemophilia patients may experience uncontrolled bleeding after an injury or a surgery. This happens because of the deficiency of clotting factors in the blood. Excessive bleeding (both exterior and internal) happens after any accident or damage when blood cannot clot correctly.

Complete answer:
This question can be solved by putting the logic of X linked inheritance, which is defined as the inheritance of genes present on only X chromosome.
Humans have $46$ chromosomes; one half of this set is derived from the mother while the other half is derived from the father. Males have a single “X” and a single “Y” chromosome, whereas females have two “X” chromosomes (XX) (XY). Mutations on the X-chromosome are connected to X-linked diseases. Because females have an extra X chromosome that functions as a "back-up," these diseases afflict men more frequently than females.
Because males only have one X chromosome, haemophilia is caused by a mutation in the factor VIII or IX gene. “Carriers” are females who have a mutation on one X chromosome.
Thus, due to the presence of a single copy of X chromosome in males makes them much more susceptible to inherit the disorder.

Note:
Hemophilia A and B have an X-linked recessive inheritance pattern. The X chromosome, which is one of the two sex chromosomes, contains the genes related with these diseases. Hemophilia A (also known as classic haemophilia or factor VIII deficiency) and haemophilia B are the two most common forms (also known as Christmas disease or factor IX deficiency).