KHORANA, HAR GOBIND

born Jan. 9, 1922, Raipur, India Har Gobind Khorana. Indian-born American biochemist who shared the Nobel Prize in Physiology or Medicine in 1968 with Marshall W. Nirenberg and Robert W. Holley for research that helped to show how the nucleotides in nucleic acids, which carry the genetic code of the cell, control the cell's synthesis of proteins. Khorana was born into a poor family and attended Punjab University at Lahore and the University of Liverpool, England, on government scholarships. He obtained his Ph.D. at Liverpool in 1948. He began research on nucleic acids during a fellowship at the University of Cambridge (1951) under Sir Alexander Todd. He held fellowships and professorships in Switzerland at the Swiss Federal Institute of Technology and the universities of British Columbia, Can. (195259), and Wisconsin, U.S. In 1971 he joined the faculty of the Massachusetts Institute of Technology. In the 1960s Khorana confirmed Nirenberg's findings that the way the four different types of nucleotides are arranged on the spiral staircase of the DNA molecule determines the chemical composition and function of a new cell. The 64 possible combinations of the nucleotides are read off along a strand of DNA as required to produce the desired amino acids, which are the building blocks of proteins. Khorana added details about which serial combinations of nucleotides form which specific amino acids. He also proved that the nucleotide code is always transmitted to the cell in groups of three, called codons. Khorana also determined that some of the codons prompt the cell to start or stop the manufacture of proteins. Khorana made another contribution to genetics in 1970, when he and his research team were able to synthesize the first artificial copy of a yeast gene.