Question

Haemophilia does not occur in women
A. It is autosomal recessive
B. Women have to be homozygous which is fatal
C. They have only one X chromosome
D. They are more resistant to this disorder

Answer 1

Hint: It is a disorder in which blood doesn’t clot properly. When the blood cannot clot properly, excessive bleeding (external and internal) occurs.

Complete answer:
Haemophilia is a X-linked recessive disorder and shows its transmission from normal carrier female (heterozygous) to male progeny. There is a presence of defective form of blood clotting factor due to which blood fails to coagulate. The person suffering from this disease cannot synthesize a normal blood protein called antihemophilic globulin (AHG) required for blood clotting.
There are two types of haemophilia:
> Haemophilia A (more severe)
> Haemophilia B
Symptoms:
> Large and deep bruises.
> Joint pain and swelling
> Blood in urine or stool
> Unexplained episodes of bleeding
The possibility of a female having haemophilia is extremely rare because the mother of that female has to be a carrier and the father should be haemophilic. Females are carriers.
1 normal girl : 1 carrier girl
1 normal boy : 1 haemophilic boy
Haemophilic female dies before birth. The haemophilic gene is present on the X chromosome and is recessive. It remains latent in carrier females.

So the correct answer is option B.

Note: Christmas disease (Haemophilia B) occurs due to absence of plasma thromboplastin and inheritance just like Haemophilia A.