David Baltimore won the Nobel Prize in physiology or medicine in 1975. He shared the award with the virologist Renato Dulbecco and the oncologist Howard Temin for the ground-breaking discovery that genetic information doesn't just travel from DNA (deoxyribonucleic acid, which contains genetic information) to RNA (ribonucleic acid, which communicates DNA information to proteins), although that concept had been at the heart of modern genetic theory. Rather, Temin and Baltimore independently discovered that some viruses could replicate their RNA into the DNA of healthy cells, causing tumors. This process is known as reverse transcription and is catalyzed by the enzyme reverse transcriptase. Its implications had a great effect on the study of cancer and the role of viruses in causing the disease. Born March 7, 1938, in New York City to Richard Baltimore and Gertrude Lipschitz, David was a gifted student of science. While still in high school he attended a...