A colour-blind man marries a woman with normal sight who has no history of colour blindness in her family. What is the probability of their grandson being colour blind? (consider the grandsons only through son)

1. 0.5

2. 1

3. Nil

4. 0.25

A man whose father was colour blind marries a woman who had a colour blind mother and a normal father. What percentage of male children of this couple will be colour blind?

1. 25%

2. 0%

3. 50%

4. 75%

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

1. 100%

2. 0%

3. 25%

4. 50%

If a colourblind woman marries a normal-visioned man, their sons will be:

1. all normal visioned

2. one-half colourblind and one-half normal

3. three-fourths colourblind and one-fourth normal

4. all colourblind