Medical students used to think of genetics as a minor curiosity - the preserve of monks and fruitflies - something to flirt with briefly in the first year before moving on to more important business. To this day my GP tells me rather proudly that he has never seen a patient with cystic fibrosis, which is one of the most common genetic disorders in Northern Europe. So why bother with genetics?

The answer lies in the technological revolution on the past 20 years. This has allowed us to understand the molecular pathology of an ever expanding host of inherited and cogenital disorders. We can now provide patients and their families with accurate testing and prenatal diagnosis, which they can use to make critical choices about their lives and the planning of their families. Technology even offers patients the promise of novel forms of treatment by supplying them with copies of the healthy functional gene which they lack.

There are two main branches of laboratory genetics. Clinical cytogenetics involves the microscopic analysis of chromosomal abnormalities such as an increase or reduction in the number of chromosomes, or a translocation of part of one chromosome to another. Molecular genetics uses the tools of DNA technology to analyse mutations in genes. The distinction between these two disciplines has become increasingly blurred by the advent of molecular cytogenetics, which makes use of DNA hybridisation to detect subtle chromosomal abnormalities such as microdeletions. A postgraduate scientific qualification instead of, or in addition to, a medical degree, is, I believe, an essential component of preparation for a senior career in laboratory genetics.

I migrated from medical biochemistry to molecular genetics, lured by the stunning advances in recombinant DNA technology of the late 1970s which led to the cloning of many of the genes that are mutated in the major genetic disorders. I remember the excitement of my first prenatal diagnosis result for thalassaemia which I obtained three weeks after an amniocentesis; two weeks were needed for culturing the cells and one week for Southern blotting, to detect the DNA polymorphisms which specified which of the parental copies of the ß globin gene the fetus had inherited. Ten years later we were turning around first trimester prenatal diagnoses in 48 hours, using polymerase chain reaction amplification of DNA extracted from a chorionic villus biopsy specimen.

As we approach the end of the millennium, genetics is moving on from the rare Mendelian disorders to the identification of genes which predispose to common diseases such as breast cancer and diabetes. This may lead to population screening to identify those at high risk, and more effective prevention by modifications to lifestyle and diet.

For further information on training programmes, please contact the Postgraduate Education Department on 020 7451 6741 or email education@rcpath.org

Chris Mathew

The College Specialty Advisory Committee on Genetics