Your article ends with the claim that “a color-blind person and a noncarrier have no chance of having a color-blind child.” Yet as I recall from basic biology class, color blindness is considered a prime example of a sex-linked trait, which makes the above statement untrue. Carried on the X chromosome, the trait would manifest differently depending on whether the offspring were male or female. Please clarify.

Elizabeth Bakwin
Chicago, Ill.

The color-blindness mutation of people on Pingelap is found on chromosome 8. The other known mutation leading to achromatopsia, this form of color blindness, is on chromosome two. While some forms of color blindness are sex linked, this one isn’t .–N. Seppa