Question

The gene for haemophilia is located on 'x' chromosome. Hence it is normally impossible for a:

• A. haemophilic father to pass the gene to his daughter
• B. carrier mother to pass the gene to her daughter
• C. carrier mother to pass the gene to her son
• D. haemophilic father to pass the gene to his son

Hint:

Always remember: Fathers give "X" to daughters and "Y" to sons. Mothers give "X" to both. This is why sex-linked traits like haemophilia often skip from a grandfather to a grandson via a carrier daughter.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Haemophilia is an X-linked recessive disorder. Inheritance follows a "criss-cross" pattern because of how sex chromosomes are passed from parents to offspring.
Step 2: Detailed Explanation:
1. Father's Contribution: A father (\(XY\)) passes his Y chromosome to his sons and his X chromosome to his daughters. 2. Mother's Contribution: A mother (\(XX\)) passes one of her two X chromosomes to both her sons and daughters. 3. Logical Deduction: Since the gene for haemophilia is on the X chromosome, a father cannot pass it to his son because the son only receives the Y chromosome from him. A son's X chromosome comes exclusively from his mother. 4. Therefore, it is impossible for a haemophilic father to pass the haemophilia gene directly to his son.
Step 3: Final Answer
It is impossible for a haemophilic father to pass the gene to his son.