Read the following passage and answer the questions that follow : Haemophilia is a sex-linked recessive disease. Study the pedigree analysis given below showing the inheritance of the disease in a family and answer the questions that follow :
(c) (ii) Why is haemophilia categorised as a Mendelian disorder ?
Show Hint
It results from a single gene change and is inherited by Mendelian rules, so it is a Mendelian disorder.
Step 1: Meaning of a Mendelian disorder:
A Mendelian disorder is caused by a change (mutation) in a single gene.
Such disorders follow Mendel principles of inheritance and can be traced in a pedigree.
Step 2: Apply to haemophilia:
Haemophilia is caused by a defective single gene on the X chromosome, which controls a blood clotting factor.
The allele is recessive and its pattern of transfer follows the same rules as Mendel traits.
So it is a Mendelian disorder.
Final Answer:
Haemophilia is caused by a mutation in a single gene and is inherited according to Mendel principles, so it is a Mendelian disorder.
