1(viii)
A family has a history of colour blindness. During genetic testing, it was found that the mother is a carrier of colour blindness (XCX) and the father has normal vision (XY). What is the probability of their sons being colour-blind?
- (a)25%
- (b)50%
- (c)75%
- (d)0%
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50%
Reason —
| Normal father (XY) | ||
|---|---|---|
| X | Y | |
| Carrier mother (XC) | XCX Carrier daughter | XCY Colour-blind son |
| Carrier mother (X) | XX Normal daughter | XY Normal son |