Question

Of a normal couple, half the sons are hemophiliac while half the daughters are carriers. The gene is located on

• A. Y ­chromosome of father
• B. X­ chromosome of father
• C. both the X ­chromosomes of mother
• D. one X­ chromosome of mother

Answer 1

The correct option is D

one X­ chromosome of mother

The correct option is D.

Explanation for the correct option:

1. Haemophilia is a sex-linked disease.
2. One of the two sex chromosomes, the X chromosome, contains the genes linked to these diseases.
3. One mutated copy of the gene in each cell is sufficient to induce the disease in males (who have only one X chromosome).
4. In the given case where half the sons are haemophilic and half the daughters are carries this possible only when the gene responsible for haemophilia is located on one X-chromosome of mother.

Final answer:Of a normal couple, half the sons are hemophiliac while half the daughters are carriers. The gene is located on one X­ chromosome of the mother.