A gene in fruit flies favors the birth of females, until another gene comes along to restore balance between the sexes. (p. 293)

DNA near the ends of people's chromosomes shows surprisingly large differences from the corresponding DNA in other great apes. (p. 302)

People with a newly discovered genetic variation are more vulnerable to HIV infection. (p. 302)

Greater understanding of the role of genetics in human diseases presents scientists with ethical dilemmas. (p. 302)

Snippets of RNA that regulate gene activity play a role in muscle-wasting diseases such as muscular dystrophy. (p. 244)

The action of a stress hormone could be why emotionally charged events form especially vivid and durable memories. (p. 254)

Mutant bacteria thrive by freeloading off their hard-working kin, but these slackers revert to working normally if they become too numerous. (p. 254)

Primates, like other mammals, possess specialized retinal cells that detect motion. (p. 230)

Decline of an important anti-cancer gene could contribute to increased cancer risk among the elderly. (p. 213)

By depleting an essential amino acid and releasing a toxin, cancer cells can ward off attack by the immune system. (p. 196)

The malaria parasite's reliance on a sugar in the gut of mosquitoes may offer a way to block the disease's transmission. (p. 206)

Rice with an added gene needs less water and can survive drought. (p. 205)

A gene that normally helps cells overcome stress can also promote cancer, perhaps offering a new target for cancer treatment. (p. 179)

Some viruses create cocoonlike refuges in the cells they invade, shielding them from the cell's defense mechanisms. (p. 157)