Women have two X chromosomes, and a normal copy of the gene will override the defective one.

WSJ: New Outlook for Colorblindness

We counted the number of times we saw a copy of a gene in normal tissue and then in the diseased one, says David Searls, SmithKlines director of bioinformatics.

FORBES: A hail of silver bullets

In this version of the study, half of the people received the normal photograph, and the other half received a blurry copy of the photograph.

FORBES: Why Do Patients Take Their Doctor's Advice?