CANCER: ABOUT DNA

From 1953 to 1970, knowledge was steadily gained about DNA, the genetic code and other complicated chemical substances within the cell, and the new science of molecular biology was born. Progress was steady but quite slow because of the difficulties in unravelling the appropriate parts of the coding system. It became clear that, within the cell itself, the chemically coded message in the DNA is transcribed into a sequence on another substance called RNA, RNA can be thought of as a messenger substance which then carries that information out from the centre of the eel) to all other parts of the cell, where it is translated into the protein form. Slowly, the way in which this occurs was being unravelled.

During the 1970s and early 1980s a series of powerful new techniques became available in the laboratories of molecular biologists. Rapid methods for discovering the sequence in DNA were devised. Special chemical substances called enzymes which could be used to cut and rejoin DNA in particular places became available, making it possible to move segments of DNA around almost at will. The means of taking segments of DNA and linking them into the genetic material of microbes followed on from these discoveries. This allowed methods to be devised for growing large quantities of DNA in the laboratory - the process which became known as gene cloning. Powerful techniques became available to probe the DNA of an organism to find the presence of particular sequences and then describe their alterations. Most recently, in the mid-1980s, techniques have been devised which allow the specific amplification of interesting segments of DNA from within any cell to be carried out rapidly in the laboratory. Increasing sophistication in laboratory automation has meant that all of these methods can now be applied reliably and quite rapidly to answer important biological questions.

The application of these powerful laboratory techniques has led to a great explosion of knowledge about the behaviour of cells and the operation and control of the genetic code. Biology, which underwent a revolution through the evolutionary theory of Darwin, has been revolutionized yet again and is now quite commonly referred to as 'the new biology'. This new biology is very different from the description of the behaviour of cells which preceded it and it has of course been applied energetically to studying cancer.

Knowledge about the control of the process of proliferation in cells and differentiation in normal cells has gone hand in hand with knowledge about the disorder of these processes in the cancerous cell. Although the understanding of the behaviour of the cancer cell is far from complete, the application of the new biology has led to a knowledge of cancer far in advance of anything available ten years ago.

*6\194\4*

Cancer