question_answer

A colourblind man marries the daughter of another colourblind man whose wife has a normal genotype for colour vision. In their progeny

A)  all the children would be colourblind

B) all their sons are colourblind

C)  none of the daughters would be colourblind

D) half of their sons and half of their daughters would be colourblind.

Correct Answer: D

Solution :

: Colourblindness is a X-linked recessive disorder. It shows criss-cross inheritance. A colourblind man has a genotype \[{{X}^{c}}Y\]. Thus, the man considered here has genotype \[{{X}^{c}}Y\]. He married daughter of a colourblind man \[({{X}^{c}}Y)\] and a normal woman \[(XX)\], thus, his wife should have \[{{X}^{c}}X\] genotype. The genotypes of their children can be worked out as follows: Thus, 50% of their sons and 50% of their daughters would be colourblind.