Question

What is the probability when both parents with blood type 'A' and normal vision (not colourblind) produce their 1st son, who has blood type 'O' and is colour blind?

• A. 1/2
• B. 1/4
• C. 1/8
• D. 1/16

Hint:

Blood type O: Requires both parents to be heterozygous (AO × AO).
Colour blindness: X-linked recessive.
Probability = Product of independent probabilities.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
This question tests knowledge of probability in genetics, involving both blood type and sex-linked inheritance.

Step 2: Key Formula or Approach:
Blood type A can be AA or AO.
For a child to have blood type O, both parents must be heterozygous (AO × AO).
Colour blindness is X-linked recessive (Xc).
A normal vision father must be X^C Y.
A normal vision mother can be X^C X^C or X^C X^c.

Step 3: Detailed Explanation:
For blood type O:
- Parents: AO × AO (both must be heterozygous).
- Probability of O child = 1/4.
For colour blindness:
- Father: X^C Y (normal vision).
- Mother: X^C X^c (carrier) to produce a colour-blind son.
- Probability of colour-blind son from carrier mother = 1/4 (1/2 chance of son × 1/2 chance of X^c).
Probability of son being blood type O and colour blind:
= \(1/4 \times 1/4 = 1/16\).
Thus, the probability is 1/16.

Step 4: Final Answer:
Thus, the probability is 1/16, which corresponds to option (D).
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