Answer
See Explanation
Work Step by Step
Genotype here is:
- man : affected ( XcY).
- women: carrier ( XcX).
Marriage of affected man with carrier women
- XcX & XcY ---------
XcX ( carrier female)
XcXc ( affected female)
XY ( normal male)
XcY ( affected male)
so, the result of marriage of acolor blind man & acarrier women is :
I- sons: 50% affected ( color blind)
50% normal ( normal vision)
II- daughters: 50% carrier ( normal vision)
50% affected ( color blind)
i.e
parents: XcX , Xcy.
eggs: 1/2 Xc & 1/2 X.
sperms : 1/2 Xc & 1/2Y.
offspring : 1/4 XcXc ( affected female)
1/4 XcX ( carrier female)
1/4 XcY ( affected male)
&1/4 XY ( normal male).
- the chance that first son will be color blind is
(1/4) = 25%
- the chance that first daughter will be color blind
is (1/4)= 25%
- if they have 4 children the chance that 2 sons
will be color blind is 0%.
