Читать книгу Your Body - The Fish That Evolved - Dr. Keith Harrison - Страница 12

The situation with blood groups is complicated enough, but for most of our genes it gets worse. It may be that few features are controlled by just one gene (or correctly one gene pair) which we can conveniently label as an ‘eye-colour gene’ or a ‘height gene’. For most characteristics, it seems many genes contribute to the final result, and they do this by interacting with each other. Eye colour is now known to be influenced by at least three different gene pairs, although there is a suspicion many more are involved. Skin colour is also controlled by more than one gene and this will probably be true for most aspects of our body.

Nor does the complexity stop there. It would be wrong to see the body simply as a machine, programmed by genes and built piece by piece like bolting prefabricated elements together. In biological systems such as ourselves, the parts are not stiff and dead like the components of an engine. Not only do the genes collaborate to create the elements for our body, but during our development as embryos these elements also interact with each other and affect how each develops. Skin may develop as skin not just because it has genes telling it to become skin but because neighbouring cells confirm this instruction and tell it what sort of skin to become. If it is on the scalp, it may become skin with hair. If it is in our mouths, it may become thin, hairless skin with glands to keep it moist. Both types of skin have the same genes; virtually every cell in our body has the same genes. We should not assume the genes in a cell inside the mouth and the genes in a cell on the back of the head know where they are in the body. Many tissues may develop as they do, not because of the genes they contain but because of the other tissues that surround them. Our bodies are more than just the products of an assembly line, they are the result of an integrated community of cells and tissues growing and communicating throughout our lives, and never more so than when we are still in the womb.

With such layers of complexity contributing to the final result, the current attempts in some laboratories to locate one ‘baldness gene’ or one ‘homosexuality gene’ (both reported in the media in recent years) are almost certainly wild goose chases.