A normal-­visioned man whose father was colour­-blind marries a woman whose father was also colour-­blind. They have their first child as a daughter. What are the chances that this child would be colour­-blind?

Explanation

Color blindness is an X-linked recessive trait. The father, who is normal-visioned, has an X chromosome with the normal vision allele (XN) and a Y chromosome. The mother, being a carrier due to her color-blind father, has one XN and one Xc. Their daughter inherits XN from her father and either XN or Xc from her mother. Therefore, she will be either normal (XNXN) or a carrier (XNXc), but not color-blind, as she doesn't inherit two Xc alleles. This makes the chance of her being color-blind 0%. The other options are incorrect because they do not accurately represent the genetic inheritance pattern for this X-linked trait.