Q.
A normal-visioned man, whose father was colourblind, marries a woman whose father was also colourblind. They have their first child as a daughter. What is the chance that this child would be colourblind?
If a normal visioned man marries a woman whose father was also colour blind. Then his wife would be carried of this disease if her mother was normal. This trait is passed into children but daughters produce by this couple are carriers, not the colour blind. 50% of sons would be colour blind.