Ever wondered why the genetic code is the way it is and exactly the same for most organisms? The explanation might come from this article, which arrives at the conclusion that the genetic code is best at encoding higher information apart from translating nucleotide triplets into amino acids.
It has already been known that the genetic code probably evolved to minimise the probability of misreads during translation by giving similar codons to the same or similar amino acids.
So what other sequence information is relevant within the coding region? Splicing sites, for instance, or sequences influencing the secondary structure of mRNA and the regular binding of histones. Also, some regulatory proteins bind to the coding region.
Of course, this calls for conflicts between the encoding of proteins on the one hand and this additional information on the other hand. The genetic code seems to minimize these conflicts.
The main reason, however, for the code to arise is thought to lie in the properties of stop codons:
first, when a frame-shift occurs during translation the probability for creating a stop codon is maximised. This is important, because otherwise the ribosome might create a useless or even harmful protein;
second, when you frame-shift a stop codon you get common codons instead of rare ones or even other stop codons. This seems to increase the higher-level information content of the genetic code.
Original paper:
Itzkovitz, S. & Alon, U. The genetic code is nearly optimal for allowing additional information within protein-coding sequences. Genome Res. 9 February 2007
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