( the genetic code is that there are grou...)Scientists crack 40-year-old DNA puzzle and point to 'hot soup' at the origin of life

The new theory builds on an original idea suggested by Francis Crick - one of the discoverers of the structure of DNA - that the three-letter code evolved from a simpler two-letter code, although Crick thought the difference in number was simply an accident "frozen in time".

The University of Bath researchers suggest that the primordial 'doublet' code was read in threes - but with only either the first two 'prefix' or last two 'suffix' pairs of bases being actively read.

By combining arrangements of these doublet codes together, the scientists can replicate the table of amino acids - explaining why some amino acids can be translated from groups of 2, 4 or 6 codons. They can also show how the groups of water loving (hydrophilic) and water-hating (hydrophobic) amino acids emerge naturally in the table, evolving from overlapping 'prefix' and 'suffix' codons.

"When you evolve our theory for a doublet system into a triplet system, you get an exact match up with the number and range of amino acids we see today," said Dr van den Elsen, who has worked with Dr Stefan Babgy and Huan-Lin Wu on the theory.

"This simple theory explains many unresolved features of the current genetic code. No one has ever been able to do this before, so we are very excited."

The theory also explains how the structure of the genetic code maximises error tolerance. For instance, 'slippage' in the translation process tends to produce another amino acid with the same characteristics, and explains why the DNA code is so good at maintaining its integrity.

"This is important because these kinds of mistakes can be fatal for an organism," said Dr van den Elsen.
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Source:University of Bath