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Khorana, Har Gobind

synthesis code codons dna

[ko rah nah] (1922– ) Indian–US molecular biologist: co-discoverer of genetic code and first synthesizer of a gene.

Educated at universities in the Punjab, at Liverpool, Zürich and Cambridge, Khorana moved to Vancouver in 1952 and extended his work in the area he had studied in Cambridge; the synthesis of nucleotide coenzymes. From 1960–70 he was at Wisconsin, and while there he carried out valuable syntheses of polynucleotides with known base sequences. These were of great value in establishing the ‘genetic code word dictionary’. This refers to the fact that the four bases (A,C,G and T) present in DNA chains are ‘read’ in linear groups of three (codons), as was known by the late 1950s. It was also known that the sequence is non-overlapping and ‘comma-less’. Since four bases in groups of three allow 43 = 64 combinations, but these code for only 20 amino acids which make up proteins, it would appear that some codons are ‘nonsense codons’ and/or some amino acids are coded by more than one codon.

Khorana had a major part in the work which established the dictionary, by his synthesis of all the 64 codons. This was an essential step in the further development of molecular biology. It turns out that the first two bases in a codon triplet are the main determinants of its specificity. Khorana’s continued work on RNA and DNA has included the synthesis in 1970 of a DNA from Escherichia coli , a gene with 126 nucleotide base pairs. He was at the Massachusetts Institute of Technology from 1970 and shared a Nobel Prize in 1968 with M W Nirenberg (1927– ) and R W Holley (1922–93), who also made major contributions to this area.

Khorasani, Nushin Ahmadi (1967–) - PERSONAL HISTORY, INFLUENCES AND CONTRIBUTIONS, BIOGRAPHICAL HIGHLIGHTS, PERSONAL CHRONOLOGY:, THE WORLD’S PERSPECTIVE, LEGACY [next] [back] Khnumhotep - PRIEST AND DANCER., SOURCES

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