science & techNLM Circulating Now1961-1965
Molecular Biology Behind the Blackboard
The genetic code is a dictionary in which sequences of three DNA or RNA bases each specify one amino acid. Marshall Nirenberg and Heinrich Matthaei cracked it in the early 1960s by making artificial RNA made only of uracil and feeding it to a cell-free system that builds proteins. The result was a chain of phenylalanine, so the three-letter word UUU stood for that amino acid. Repeating the experiment with other base mixtures, they matched all the combinations to the twenty amino acids by 1965.
Cells build proteins by reading messenger RNA in groups of three bases called codons. Each codon tells a ribosome which amino acid to add next. By supplying a synthetic RNA with known bases and seeing which amino acids were linked, the researchers worked out the assignment for each codon.
Cracking the code showed that all living things read genes with the same dictionary, a foundation for modern biology and genetic engineering. Nirenberg shared the 1968 Nobel Prize in Physiology or Medicine for the work.
Nirenberg shared the 1968 Nobel Prize with Robert Holley and Har Gobind Khorana.
U.S. National Library of Medicine
Illustrative photo · The original uploader was Sverdrup at English Wikipedia . V…, Public domain, via Wikimedia Commons
