S.L. Miller’s experiment –
• He created electric discharge in a closed flask containing CH4, H2, NH3 and water vapour at .
• The conditions were set similar to those of the primitive atmosphere in the laboratory.
• He observed formation of amino acids while in similar experiments performed by other scientists the presence of complex molecules like- sugar, pigments, nitrogen bases and fats in the flask were also observed.
Salient features of genetic code –
i. The codon is triplet. 61 codons code for amino acids and 3 stop codons do not code for any amino acids, hence they function as stop codons.
ii. One codon codes for only one amino acid, hence, it is unambiguous and specific.
iii. Some amino acids are coded by more than one codon, hence the code is degenerate.
iv. The codon is read in mRNA in a contiguous fashion. There are no punctuations.
v. The code is nearly universal i.e. UUU codes for Phenylalanine from bacteria to humans.
vi. AUG has dual functions. It codes for Methionine (met) and it also acts as initiator codon.
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