Marshall Warren Nirenberg (1927-2010), US biochemist. Nirenberg trained as a biologist, but developed an interest in biochemistry and obtained his PhD in that area in 1957. He worked on enzymes, and from 1959 studied the enzymes involved in DNA and RNA (the genetic molecules). From 1962 he was head of Biochemical Genetics at the US National Institutes of Health. He shared the 1968 Nobel Prize in Physiology or Medicine for his work on genetics. Official NIH (National Institutes of Health) portrait taken circa 1968.