Evolutionary explanation for the "degenerate" genetic code

[nativecoder]

Hi again,

 

I have some philosophical questions here.

 

Context: In the genetic code we have 64 different codons to codify 20 aminoacids + 3 STOPs + 1 START (shared with the methionine AA). So we say the genetic code is degenerate, having information redundancy (18 of the AAs are specified by 2 or more codons). Most of the synonymous condos only differ in the last nucleotide (due to the properties of mRNA and tRNA).

 

However, is there any evolutionary explanation for this? Something like: is a protective measure against "evil" mutations related to important AAs (e.g. UC? always codifies "serine" -being ? any nucleotide- because if you change serine in a protein it really gets hurt).

 

The second questions is: Do we have any clue if this coding system has been always this way?

 

Many thanks

Regards