Explain the concept of the genetic code.

(N/A) The genetic code is the relationship between the sequence of amino acids in a polypeptide chain and the sequence of nucleotides on $m-RNA$.
During replication and transcription,a nucleic acid is copied into another nucleic acid. In the process of translation,genetic information is transferred from a polymer of nucleotides to a polymer of amino acids.
Changes in nucleic acids (genetic material) lead to changes in the amino acids of proteins. This led to the proposal of the genetic code,which determines the sequence of amino acids during protein synthesis.
The main problem was determining the exact number of nucleotides that code for a single amino acid.
There are only $4$ nitrogenous bases $(A, C, G, U)$ on $m-RNA$ to code for $20$ types of amino acids in organisms.
If the genetic code were a singlet ($1$-letter),it would only provide $4$ codes,which is insufficient to code for $20$ amino acids.
If the genetic code were a doublet ($2$-letter),it would provide $16$ codes,which is also insufficient.
George Gamow $(1954)$,a physicist,suggested that the genetic code is a triplet,meaning each code consists of three nucleotides. This results in $4^3 = 64$ possible codes,which is more than enough to code for $20$ amino acids. Later,Har Gobind Khorana,Holley,and Nirenberg provided experimental evidence for the triplet code.
Marshall Nirenberg's cell-free system for protein synthesis was instrumental in deciphering the code. Severo Ochoa's enzyme (polynucleotide phosphorylase) helped in polymerizing $RNA$ with defined sequences in a template-independent manner.