Correct option (a) Nirenberg and Matthaei
Explanation
The existence of triplet code was simply an assumption till 1961, when Nirenberg and Matthaei proved its existence by experiments. They were able to synthesise artificial mRNA, which contained only one nitrogenous base, i.e. uracil.
This synthetic poly U sequence was then placed in a cell free system containing protein synthesising enzymes (extracted from bacterium E. coli) and 20 amino acids together with necessary ATP. During the process, a small polypeptide molecule was produced, which was formed by the linking of phenylalanine.
This suggested that UUU is the code for phenylalanine. Nirenberg got Nobel prize for his contributions.
