(1927–2019) South African–British molecular biologist
The son of a Lithuanian exile, Brenner was born in Germiston, South Africa, and educated at the universities of Witwatersrand and Oxford, where he obtained his DPhil in 1954. In 1957 he joined the staff of the Medical Research Council's molecular biology laboratory in Cambridge.
Brenner's first major success came in 1957 when he demonstrated that the triplets of nucleotide bases that form the genetic code do not overlap along the genetic material (DNA). The basic idea was that the amino-acid sequence of a protein is determined by the sequence of the four nucleotides – A, T, C, and G – in the DNA, with a specific amino acid being specified by a sequence of three nucleotides. Thus, in an overlapping code the sequence:
A T T A G T A C G T C G A....
would yield the following triplets, ATT, TTA, TAG, AGT, GTA, etc., each of which specified a particular amino acid.
Brenner however pointed out that such a code imposed severe restrictions on the permitted order of bases. ATT, for example in an overlapping code, could be followed by the four bases TTA, TTT, TTC, and TTG only. This was relatively easy to test without in any way understanding the true nature of the code, and it was soon shown that such implied restrictions were frequently broken.
A greater triumph followed in 1961 when Brenner, in collaboration with Francis Crick and others, reported the results of careful experiments with the bacteriophage T4, which clearly showed that the code did consist of base triplets that neither overlapped nor appeared to be separated by ‘punctuation marks’.
The same year also saw Brenner, this time in collaboration with François Jacob and Matthew Meselson, introducing a new form of RNA, messenger RNA (mRNA). With this came one of the central insights of molecular biology – an explanation of the mechanism of information transfer whereby the protein-synthesizing centers (ribosomes) play the role of nonspecific constituents that can synthesize different proteins, according to specific instructions, which they receive from the genes through mRNA.