A male who has normal vision marries a woman who is colorblind. What percentage of  their male offspring will be colorblind?

Colorblindness is a sex-linked trait that is located on the X chromosome. Males only have one X chromosome, which they receive from their mother, and one Y chromosome, which they receive from their father.

Here are the steps to answer the question:

1. The male who has normal vision will have an X chromosome with the normal vision gene and a Y chromosome. We'll represent this as XY.

2. The woman who is colorblind will have two X chromosomes both carrying the colorblind gene because she is colorblind. We'll represent this as XcXc.

3. When they have offspring, the male will pass on either his X or his Y chromosome. The female will pass on one of her Xc chromosomes.

4. Therefore, the possible combinations for their offspring are XcY and XcX.

5. The XcY combination represents a male child who is colorblind, because he received the colorblind gene from his mother and a Y from his father. The XcX combination represents a female child who is a carrier of the colorblind gene, because she received one colorblind gene from her mother and a normal gene from her father.

6. Therefore, 100% of their male offspring will be colorblind, because the only possible combination for a male child is XcY.