Jeremy Ahouse sends me an amazingly good story from The Scientist about protein folding. As you know, proteins are made of a long chain, or chains, of amino acids folded up on themselves in complicated ways to make nubbly shapes, like an armchair modelled out of macaroni. The chains are assembled one link at a time by mRNAs which read off a triplet codon from the DNA and fetch the corresponding amino acid to attach it. So think of a piece of spaghetti emerging and coiling up as it does so. But different codons can code for the same amino acid, and so there are different mRNAs that do the same thing.
since the sequence of the protein is the same, an allele which differs from another only in the codons it uses to represent the same amino acids is regarded as being the same gene. The change can be significant for things like DNA fingerprinting, but not, it was thought, for anything else.
What the paper argues is that proteins made with rarer codons (for the same amino acid) may fold differently to those made with more common ones; and since the funcion of proteins is actually determined by their shape, they work differently, too. In particular, the researchers looked at a protein which helps pump anti-cancer drugs through cell walls, and found that some forms worked much worse than others with the same drugs.
It’s all a bit tentative as yet, and I may have got some or all of the details right, but it is a wonderful indication of just how complicated the meccano of life must be.