How Many Sparks in the Genome?

Less than two percent of the human genome is made up of protein-coding genes. Fifty years ago, scientists launched an expedition of the other 98 percent. It has been a slow march for much of that time, but in recent years the pace has picked up, thanks to advances such as new ways to sequence DNA. Scientists are now generally agreed that some of the non-coding DNA falls into several categories, including

–sites where proteins can bind in order to switch nearby genes on and off

–genes for RNA...