A colour blind girl is rare because she will be only when :

Options

A. her mother and maternal grandfather were colourblind
B. her father and maternal grandfather were colourblind
C. her mother is colour blind and father has normal vision
D. parents have normal vision but grand parents were colourblind

Answer

B

Explanation

For a girl to be colourblind, the genotype of her father should be `X^(C )Y` and of her mother either `X^(C )X` or `X^(C ) X^(C )`, where `X^(C )` represents colour blind gene.