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Genetic Code and Regulation - Medical Science

Q1:

Which of the following techniques was carried out by Nirenberg and Matthaei in 1961 to determine the first codon?

A In vitro synthesis of a polypeptide using UUUUU

B Labeled peptide binding to a ribosome

C Mixed co-polymer mRNA synthesis

D none of the above

ANS:A - In vitro synthesis of a polypeptide using UUUUU

This was the easiest methods to find which codon codes for which Amino acid. If a sequence is generated such that it contains all Uracils or Thymines, e.g UUUU, irrespective of what the reading frame only 1 type of Amino acid will be coded and polymerised.

In the case of UUUU. It ll be a peptide having repeated units of phenylalanine as UUU codes for it. Analysing such a peptide is easy. Further variations in the repeated units led to the discovery of all codons.