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Q.
An organism uses $20$ amino acids while its $DNA$ is made up of $6$ types of nitrogenous bases. What would be the minimum size of a codon?
Molecular Basis of Inheritance
Solution:
As there are $20$ amino acids thus there must be atleast $20$ unique combinations of the bases. If the code is singlet i.e., consists of only one base then possible codons can be $(6)^{1} = 6$, which is far less than the required number i.e., $20$. If the code is doublet (made up of combination of two bases) then the possible codons can be $(6)^2 = 36. 36$ is sufficient (even more) than the required number. Here some amino acid could be coded by more than one codon and some codons will function as start and stop codons.