Scientists working out the meaning of life using test tubes have discovered a new genetic code based on four chemical letters of DNA instead of three.
Apparently it will mean that living cells could be persuaded to make proteins with properties that have never been seen in the natural world allowing for the creation of new or “improved” life forms that incorporate these materials in their tissue.
Jason Chin, at the University of Cambridge, said that in all life forms, the cell’s protein-making machinery reads the four chemical “letters” of DNA – called nucleotides – in triplets to make chains of amino acids.
Each three-letter word embodies the code for a single amino acid or tells the cell to stop making a protein chain however Chin has worked out a way of redesigning the cell’s machinery so that it can also read the genetic code four letters at a time.
This boosts the number of amino acids that can be built into a protein from the 20 covered by the existing genetic code to 276. That’s because Chin’s new code creates 256 possible four-letter nucleotide words or “codons”, each of which can be assigned to an amino acid that doesn’t currently exist in living cells. In otherwords it is a new form of genetic code.
New amino acids created using Chin’s system react with each other to form a different kind of chemical bond from those that usually hold proteins together.