Question

Degeneracy of a genetic code is generally attributed to the

• A. first member of a codon
• B. second member of codon
• C. entire codon
• D. third member of a codon

Answer 1

The correct option is D third member of a codon

The genetic code has a number of salient features. One of them states that the genetic code is degenerate. This means that some amino acids are coded by more than one codon.
In a triplet for a particular amino acid, more than one codon can be used. If there was a one to one relation between amino acids and the codons, then 44 codons out of 64 would have been useless or nonsense codons.

A code is degenerate because of the third base of the codon. For example GCU, GCC, GCG and GCA all code for alanine amino acids. Here, in all these codons, the first and the second base are fixed whereas the third base changes. But it brings about no change in the amino acid that is coded. This means, while the first and second base play an important role, third base mostly does not play such a decisive role in the determination of the amino acid that would be coded by the codon. Hence, the degeneracy of the genetic code is attributed to the third codon. This is also called the Wobble hypothesis.