When scientists announce that they have discovered a ‘gene’ for heart disease or asthma, what they really mean is that they have identified one of a number of genes that may, under certain circumstances, make an individual more or less susceptible to the action of a variety of environmental agents, some of which are known to be involved in our common intractable diseases.It appears now that molecular biology is going through some profound changes, which will make those simplistic 'one gene - one disease' stories even less believable.
It is beginning to dawn on biologists that they may have got it wrong. Not completely wrong, but wrong enough to be embarrassing. For half a century their subject had been built around the relation between two sorts of chemical. Proteins, in the form of enzymes, hormones and so on, made things happen. DNA, in the form of genes, contained the instructions for making proteins. Other molecules were involved, of course. Sugars and fats were abundant (too abundant, in some people). And various vitamins and minerals made an appearance, as well. Oh, and there was also a curious chemical called RNA, which looked a bit like DNA but wasn't. It obediently carried genetic information from DNA in the nucleus to the places in the cell where proteins are made, rounded up the amino-acid units out of which those proteins are constructed, and was found in the protein factories themselves.There follows a description of the different jobs performed by RNA. Then,
All that was worked out decades ago. Since then, RNA has been more or less neglected as a humble carrier of messages and fetcher of building materials. This account of the cell was so satisfying to biologists that few bothered to look beyond it. But they are looking now. For, suddenly, cells seem to be full of RNA doing who-knows-what.
...evolution is as much about changes in the genes for small RNAs as in the genes for proteins—and in complex creatures possibly more so. Indeed, some researchers go further. They suggest that RNA could itself provide an alternative evolutionary substrate. That is because RNA sometimes carries genetic information down the generations independently of DNA, by hitching a lift in the sex cells. Link this with the fact that the expression of RNA is, in certain circumstances, governed by environmental factors, and some very murky waters are stirred up...What is being proposed is the inheritance of characteristics acquired during an individual's lifetime, rather than as the result of chance mutations.It remains to be seen though whether medical researchers take this opportunity to rethink the complexity of the human organism as a physical, personal and social being, or whether another bout of reductionism ensues.