Colorblindness Pedigree Chart

X-linked traits are traits that are passed on from parents to offspring on the X chromosome (the chromosome related to gender). A common X-linked trait is colorblindness. The genes needed to distinguish red from green are on the X-chromosome. A female with one defective and one normal X-chromosome has normal vision. However, a male with a defective color vision gene on his X-chromosome, is colorblind. There are no genes for normal color vision on the Y-chromosome to cover for the defective X-chromosome. One way of tracing a trait through generations is a pedigree chart. Here is a colorblindness pedigree chart.

From http://library.thinkquest.org/C0110254/Xlink.html

The first pair at the top had two children. Were they male or female? Colorblind or did they have normal vision?

One of those children had children. Could those children see color normally?