How the Genetic Code was cracked. Har Gobind Khorana, 89, MIT biochemist, has died. In 1968, he shared the Nobel prize with Marshall Nurenberg and Robert Holley for working out the “blueprint of life”.
• After the structure of DNA was solved in the 50’s, the challenge was to figure out how it encoded information.
• There are 4 letters in DNA (A, C, T and G) that can be strung together in any combination or length.
• There are 20 amino acids in proteins, that can also be combined in any order.
• The minimal “codon” would need a triplet of 4 letters, giving 64 combinations (4x4x4), sufficient to code all 20 amino acids. Some have multiple codes, and there are stop codons.
• Khorana synthesized strands of precise combination of nucleotides that when translated into protein, revealed the code.
Khorana rose from humble origins from a village in India. In 1970 he painstakingly synthesized the first artificial gene that could work in a cell, a landmark achievement at the time.
An announcement, yesterday, shows the amazing progress in synthetic biology: Johns Hopkins scientists have teamed up with China’s BGI to artificially synthesize a complete eukaryotic genome, paving the way for better bioproduction of chemicals, energy and food.