Principles of Inheritance and Variation Question 174

174. A normal woman, whose father was colourblind is married to a normal man. The sons would be

[2004]

(a) $75 %$ colour-blind

(b) $50 %$ color-blind

(c) all normal

(d) all colour-blind

Show Answer

Answer : b

Hints & Solution

(b) Normal woman with colour blind father would be a carrier.

Woman $(\mathbf{X}^{c} \mathbf{X})$ $x$ Normal man (XY)
ogeny $\underset{\substack{\text{ normal } \\ \text{ but carrier } \\ \text{ daughter }}}{X^{c} X}$ $\underset{\substack{\text{ normal } \\ \text{ daughter }}}{XX}$ $\underset{\substack{\text{ colour blind } \\ \text{ son }}}{X^{C} Y}$ $\underset{\substack{\text{ normal } \\ \text{ son }}}{X Y}$
$50 %$ of the sons would be colour blind.