In humans, color-blindness is a sex-linked recessive trait. A woman who is color-blind marries a man who has normal vision.What are the chances of having a child with normal vision? A 100% B. 75% C. 50% D. 0%

To determine the chances of having a child with normal vision, we need to consider the inheritance pattern of color-blindness.<br /><br />Color-blindness is a sex-linked recessive trait, which means it is carried on the X chromosome. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).<br /><br />In this scenario, the woman is color-blind, which means she has two copies of the recessive allele for color-blindness (XX'). The man has normal vision, which means he has a normal allele on his X chromosome (XY).<br /><br />When they have a child, the child will inherit one X chromosome from the mother and either an X or Y chromosome from the father.<br /><br />If the child is a girl (XX), she will inherit one X chromosome from the mother and one X chromosome from the father. Since the mother is color-blind, the child will inherit the recessive allele for color-blindness from the mother. Therefore, the child will be color-blind.<br /><br />If the child is a boy (XY), he will inherit one X chromosome from the mother and one Y chromosome from the father. Since the mother is color-blind, the child will inherit the recessive allele for color-blindness from the mother. Therefore, the child will be color-blind.<br /><br />Therefore, the chances of having a child with normal vision are 0%.<br /><br />The correct answer is D. $0\% $.