Question

Hargobind Khorana was awarded Nobel Prize for

• A. Deciphering genetic code
• B. Artificial gene synthesis
• C. Nucleotide sequence of tRNA
• D. Discovery of transposons

Answer 1

Answer: (B)

Artificial gene synthesis

M. Nirenberg, Khorana and Holley were awarded Nobel Prize for in vitro synthesis of polypeptides using artificially synthesized mRNA. Marshall Nirenberg and Heinrich Matthaei incubated synthetic polyuridylate, poly(U), GTP, ATP, E. coli extract and a mixture of the 20 amino acids in 20 different tubes containing a different radioactively labelled amino acid. The poly(U) mRNA has many successive UUU triplets and thus the resultant polypeptide should contain only the amino acid encoded by the triplet UUU. One out of 20 tubes synthesized a radioactive polypeptide that contained radioactive phenylalanine. It was concluded that the triplet codon UUU encodes phenylalanine. Khorana used the same approach to reveal that polycytidylate, encodes a polypeptide containing only proline and polyadenylate encodes polylysine.