Sublime

Most of the cells of the body make proteins, and genes are the way we make them. We express particular genes via certain cells making particular proteins.

In the nineteenth century, the Austrian monk Gregor Mendel had shown that you could trace the transmission of a trait in plants, like height or seed shape, from one generation to the next. Scientists named whatever it was in a cell that transmitted a trait a gene, from the Greek word genos, “birth” or “clan.”

Tatum pelted colonies of E. coli with enough X-rays to kill 9,999 of every 10,000 bacteria. Among the few survivors he discovered mutants that could grow only if he supplied them with a particular amino acid. Helped along, the mutants could even reproduce, and their offspring were just as crippled. Tatum had gotten the same results as he had with