If variety lends life flavor, then humans are kicking things up to a previously unrecognized notch on the spice-o-meter. New efforts to decipher the genetic blueprints of thousands of people have turned up more than half a million tweaks in human DNA, many more than scientists expected. Most of these tweaks are new to science, and a majority fall into a class called “rare variants,” found in 0.5 percent of the population or less. Some of the variety recently uncovered is so uncommon that it shows up in people living in a single geographic region, or even in only one person. Despite their... (p. 28)

Molecular analysis yields clues about the immune system activity of a probable sacrificial victim. (p. 9)

A single genetic transformation turns mild-mannered bacteria into assassins. (p. 18)