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The identification of genes that contribute to mental diseases, such as schizophrenia and manic depression, is one of the biggest challenges facing geneticists, according to Sir Walter Bodmer, director of the Imperial Cancer Research Fund.

Giving the Romanes lecture at Oxford University last week, Sir Walter said that establishing the role of genes in such diseases is also likely to have a significant impact on the understanding of normal brain functions. A major advance will come from identifying all those genes which function specifically for the brain. He said: "The genetic approach may well turn out to be the only, or at least the most penetrating route, to a better understanding of mental disease."

In a wide-ranging lecture Sir Walter highlighted possible future applications of advances in genetics in areas such as criminal justice. He suggested that in the future it may be possible to reconstruct faces from samples of DNA, opening up the prospect of genetic technology forming the basis of future identity parades and the televising of genetically engineered features of wanted criminals and missing persons.

Industrial applications of genetic technology will continue to rise. Sir Walter said that "there can be no doubt that the pharmaceutical industry of the 21st century will be almost totally based on this new genetic knowledge". He said many new drugs will be developed and these will be derived not so much from knowledge of gene protein products themselves but overwhelmingly from the discovery of new chemicals that inhibit or stimulate the functions of newly discovered genes and their products.

The range of new functions being discovered by genetic technology is "quite extraordinary" and even old functions are being revised. Aspirin, for example, was used for nearly 25 years before it was discovered that a major basis for its activity was to inhibit a particular enzyme. New gene technology has shown that there are two versions of this enzyme. Blocking of one accounts for aspirin's effect on inflammation, helping to alleviate, for example, rheumatic pain. Blocking the second version, however, may contribute to the unwanted effect of aspirin in causing ulcers. Sir Walter said that separation of these functions means chemicals can now be sought to block the first version while not blocking the second, allowing side-effects to be avoided.