मराठी

Sex-Linked Inheritance in Human Beings - Haemophilia

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Estimated time: 4 minutes

CISCE: Class 12

Definition: Haemophilia

Haemophilia is an X-linked recessive hereditary disorder in which the blood lacks the normal clotting factor, resulting in prolonged bleeding even from minor injuries.

Maharashtra State Board: Class 12

Key Points: Haemophilia

Meaning: Haemophilia is an X-linked recessive disorder in which blood does not clot properly, causing excessive bleeding.
Cause: It occurs due to a deficiency of clotting factors (Factor VIII or IX), controlled by a recessive gene (Xʰ) on the X chromosome.
Expression in Sexes: Males (XʰY) are more commonly affected, while females are affected only if both X chromosomes carry the recessive gene (XʰXʰ); otherwise, they are carriers (XᴴXʰ).
Inheritance Pattern: It shows criss-cross inheritance, where the gene passes from the affected father to the daughter (carrier) and then to the grandson.
Example Crosses: Haemophilic male × normal female produces carrier daughters; carrier female × normal male produces 50% haemophilic sons.