Molecular biology relies heavily on genetics; traditionally many interesting properties of organisms have been studied via their inheritance, so identifying the genes responsible. Once the genes are found, how they work can be investigated using molecular biology. In human genetics, much emphasis has been on what goes wrong—i.e. the genetics of inherited disease. The full implications of this for cancer are now becoming clear, since most of these diseases carry a genetic predisposition of some kind. If these predisposing genes are identified, we have a new handle on some crucial aspects of the disease process; recently several cancer susceptibility genes have been isolated.
The Human Genome Project (a multi-laboratory collaboration to identify the DNA sequence of all the genes in an organism) is now complete; the task of identifying genes will become routine. Linking these genes with certainty to the risk of diseases such as cancer is still problematic: there are many other factors involved (e.g. environmental).
The Human Genome Project has shown the DNA sequence for 30 000 genes. Most are novel with no resemblance to a gene of known function. The amino-acid sequence of the protein product is predictable, but current methods do not lead to a prediction of the three-dimensional structure of the protein. Once possible, there will still be great difficulties in defining the role of novel gene products in the organism's biology.
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