Question

Choose the correct answer from the alternatives given :
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?

• A. 6
• B. 4
• C. 3
• D. 2

Answer 1

Answer: (D)

2

As there are 20 amino acids thus there must be at least 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.

So, the correct answer is ''2'.