Question

A normal woman whose father was colourblind is married to a normal man, (assuming equal distribution of female gametes), then _________.

• A. \(50\%\) of their sons will be colourblind.
• B. All the sons will be colourblind.
• C. All the sons will be normal.
• D. \(75\%\) of the sons will be colourblind.

Hint:

Colour blindness is X-linked recessive; the woman must be a carrier because her father was colourblind.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Colour blindness is an X-linked recessive trait. Let the normal allele be \( X^{C} \) and the defective one \( X^{c} \).

Step 2: Find the parent genotypes
The colourblind father \( X^{c}Y \) gave his only X to his daughter, so the normal woman is a carrier \( X^{C}X^{c} \). Her husband is normal, \( X^{C}Y \).

Step 3: Calculation
Sons get their X from the mother: half receive \( X^{C} \) (normal) and half receive \( X^{c} \) (colourblind). So \( 50\% \) of the sons are colourblind.

Final Answer:
Half of the sons, that is 50 percent, will be colourblind. \[ \boxed{\text{(A) }\text{50\% of their sons will be colourblind.}} \]