he first step in solving this problem requires an examination of the possible genotypes of the parents. As stated color-blindness is a recessive linked trait. So the genotypes of the parents should be:
mother's genotype (normal vision but whose father was color blind) XNXn
She is a carrier because of her heterozygous condition. For the recessive gene to be expressed one must be homozygous for it.
father's genotype (color blind) XnY
