As the DNA 'alphabet' contains four letters - called bases - there are as many as 64 three-letter words available in the DNA dictionary. This is because it is mathematically possible to produce 64 three-letter words from any combination of four letters.
But why there should be 64 words in the DNA dictionary which translate into just 20 amino acids, and why a process that is more complex than it needs to be should have evolved in the first place, has puzzled scientists for the last 40 years.
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One of quirks of the genetic code is that there are groups of codons which all translate to the same amino acid. For example, the amino acid leucine can be translated from six different codons whilst some amino acids, which have equally important functions and are translated in the same amount, have just one.
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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.
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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.
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The new theory also highlights two amino acids that can be excluded from the doublet system and are likely to be relatively recent 'acquisitions' by the genetic code. As these amino acids - glutamine and asparagine - are unable to hold their shape in high temperatures, this suggests that heat prevented them from being acquired by the code at some point in the past.
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"As the code evolved it has been possible for it to adapt and take on new amino acids. Whether we could eventually reach a full complement of 64 amino acids I don't know, a compromise between amino acid vocabulary and its error minimising efficiency may have fixed the genetic code in its current format. "
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what i want to know is how does this relate to the hebrew letters which can be seen as 22 unique entities, encoded by a 5-'letter' encoding alphabeth. [in some sense there are 5 bases (incl. uracil which isn't exactly a different base), and potentially more amino acids, but still how does it all relate?]
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