Question

A women has a colorblind father. Her son also has a colorblind father. If we considered only male offpsring, the probability of colorblindness in her son would be

• A. $100$ percent
• B. $50$ percent
• C. $0$ percent
• D. $25$ percent
• E. $75$ percent

Answer 1

The correct option is B $50$ percent

Colorblind father has passed the affected X chromosome to the woman, the genotype of carrier woman is $X^c$X. A colorblind son ($X^c$Y) should get affected X chromosome from carrier mother and Y chromosome from the father (fathers do not contribute the X-linked traits to sons). Carrier woman forms two types of gametes 1/2 carrying $X^c$ chromosome and 1/2 carrying X chromosome. Chances of fusion of egg having $X^c$ chromosome and sperms having Y chromosome 1/2 i.e. 50%. Thus, the correct answer is option B.