How did the genetic code come into existence?

(N/A) During replication and transcription,a nucleic acid is copied to form another nucleic acid. Hence,these processes are easy to conceptualize on the basis of complementarity.
The process of translation requires the transfer of genetic information from a polymer of nucleotides to synthesize a polymer of amino acids.
There is no direct complementarity between nucleotides and amino acids,nor could any be drawn theoretically.
However,there was ample evidence to support the notion that changes in nucleic acids (genetic material) were responsible for changes in amino acids in proteins.
This led to the proposition of a genetic code that could direct the sequence of amino acids during protein synthesis.
Historical background and contributions of various scientists:
$1$. George Gamow: In $1954$,a physicist named George Gamow proposed that in order to code for all $20$ amino acids,the code must be made up of three nucleotides (triplet code).
If one base coded for one amino acid,only $4$ amino acids could be coded. If a sequence of two bases coded for one amino acid,the four bases could specify only $16$ $(4 \times 4)$ amino acids,which is inadequate. But if a sequence of three bases coded for one amino acid,the four bases would specify $64$ $(4 \times 4 \times 4)$ amino acids,which is sufficient.
$2$. In the $1960$s,proof regarding the genetic code came from the research of the following scientists:
$(i)$ Har Gobind Khorana: Developed a chemical method for the synthesis of $RNA$ molecules with defined base combinations (homopolymers and copolymers).
$(ii)$ Marshall Nirenberg: Developed a cell-free system for protein synthesis that helped in deciphering the code.
$(iii)$ Severo Ochoa: Showed that the enzyme polynucleotide phosphorylase helped in polymerizing $RNA$ with defined sequences in a template-independent manner (enzymatic $RNA$ synthesis).