Question

First codon of uracil nucleotides, UUU was deciphered by

• A. Mathaei
• B. Khorana
• C. Nirenberg
• D. Both A and C

Answer 1

The correct option is D Both A and C

Marshall Nirenberg and Heinrich Mathaei 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 same approach to reveal that polycytidylate, encodes a polypeptide containing only proline and polyadenylate encodes polylysine. Correct option is D.