Question

Who gave the first experimental proof of triplet code?
A. George Gamow
B. Nirenberg
C. Kohenberg
D. Khorana

Answer 1

Hint: The experiment was performed in May, 1961. The experiment used nucleic acid homopolymers to translate particular amino acids to deduce the very first 64 triplet codons in the genetic code. The triplet code is the standard genetic code where a sequence of 3 nucleotides codes for the synthesis of a particular amino acid - the arrangement of nucleotides in DNA molecules, which transports genetic data in living cells.

Complete Step by Step Answer:
Nirenberg and Matthaei required a cell-free system for converting amino acids into proteins. Trying to follow Alfred Tissieres' work, and after several unsuccessful attempts, they generated a stable system by rupturing E. coli bacteria cells and discharging the components of the cytoplasm. This permitted them to synthesize protein, but only after the correct type of RNA was added, letting Nirenberg and Matthaei regulate the experiment. They generated synthetic RNA molecules outside of the bacterium and introduced them into the E. coli system.
The experiment employed 20 test tubes, each containing distinct amino acids. For each trial, 19 test tubes were "cold," while one was radioactively labeled to allow the scientists to observe the reaction. Every time they repeated the experiment, the "hot" amino acid changed. Nirenberg was intrigued about which amino acid would be embedded into a protein after the addition of a specific type of synthetic RNA.
On Saturday, May 27, 1961, Matthaei mixed uracil-only synthetic RNA (termed poly-U) with cell sap deduced from E. coli bacteria and incorporated it into each of the 20 test tubes. The "hot" test tube this time was phenylalanine. The results were both spectacular and simple: after an hour, the control tubes had a baseline level of 70 counts, while the hot tube had 38,000 counts per milligram of protein. The finding showed that a string of uracil repeating bases compelled a protein chain of phenylalanine repeating amino acids. The code may have been broken! Nirenberg and Matthaei's innovative experiment outcome was UUU=Phenylalanine.
The correct option is B

Note: 64 nucleotide triplets can exist, which is significantly more than the number of amino acids. UAA, UAG, and UGA are 3 stop codons. The leftover 61 codons are responsible for encoding 20 amino acids. The codon AUG encodes the amino acid methionine, which is known as the start codon.