Haemophilia is a

The correct answer is Option (2) → Sex linked recessive disorder

Option (1) Sex linked dominant disorder — Incorrect. Haemophilia is sex-linked, but it is recessive. A heterozygous female (carrier) is not affected, which would not be possible if the gene were dominant.

Option (2) Sex linked recessive disorder — Correct. The gene for haemophilia is on the X chromosome and is recessive. So the disease passes from an unaffected carrier female to some of her sons, and a female is affected only rarely.

Option (3) Autosome linked dominant disorder — Incorrect. The haemophilia gene lies on the X chromosome, not on an autosome, and it is recessive, not dominant. That is why it is much commoner in males.

Option (4) Autosome recessive disorder — Incorrect. Haemophilia is recessive, but its gene is on the X chromosome, not an autosome. An affected father passes it to all his daughters but none of his sons, a sex-linked pattern.

Note: A similar question was also asked in CUET (UG) 2026 on 25-05-2026 (Slot 1).

NCERT Extract:
Mendelian Disorders – “… Haemophilia : This sex linked recessive disease, which shows its transmission from unaffected carrier female to some of the male progeny has been widely studied. In this disease, a single protein that is a part of the cascade of proteins involved in the clotting of blood is affected. Due to this, in an affected individual a simple cut will result in non-stop bleeding. The heterozygous female (carrier) for haemophilia may transmit the disease to sons.”