Genetics often progresses by breaking things. Early experiments used naturally broken genes—mutations—to work out the basic rules. Then geneticists found out how to induce mutations with radiation and chemicals. That gave them more material to work with, but the mutations still appeared at random. Then the “knockout mouse” was invented, in which mice have specified genes rendered inoperable, thus revealing their functions. Now, as they write ineLife, John Rinn of Harvard University and his colleagues have used the idea of knockouts to prove that certain bits of DNA once regarded as junk are proper genes after all.
