Defining Genetic Code Degeneracy
The degeneracy of the genetic code refers to the biological property where multiple codons—sequences of three nucleotides on messenger RNA (mRNA)—can code for the same specific amino acid during protein synthesis. This means that an individual amino acid is often specified by more than one possible three-base sequence.
Understanding the Wobble Hypothesis
Out of the 64 possible codons, 61 code for the 20 common amino acids, while the remaining three serve as stop signals. This numerical imbalance creates redundancy. The 'wobble hypothesis' explains how a single transfer RNA (tRNA) molecule can recognize more than one codon, typically by a flexible pairing at the third nucleotide position of the codon.
An Illustrative Example
A clear example of degeneracy is the amino acid Leucine, which can be encoded by six different codons: UUA, UUG, CUU, CUC, CUA, and CUG. This wide range of codons for a single amino acid highlights how changes in the third nucleotide often do not alter the resulting amino acid, demonstrating the code's flexibility.
Importance in Biological Systems
The degeneracy of the genetic code serves as a crucial protective mechanism against point mutations. If a mutation occurs in the third position of a codon, it frequently results in a 'silent' mutation, meaning the same amino acid is still incorporated into the protein. This redundancy minimizes the potential for detrimental changes in protein function, thereby maintaining genetic stability.