Future direction of medical genetics.

The genetic revolution began in 1953 when Crick and Watson proposed the double-helix structure of DNA. On 26th June 2000, the first draft of the 3.2 billion bases of DNA (the human genome) was made public. The completion of the sequencing of human DNA, undoubtedly the greatest biological achievement will have major implications for the future direction of medical genetics and medicine. The practical value of the completed DNA sequence will be to provide more rapid approaches in the search for disease-causing genes which will lead to the unravelling the molecular basis ofdisease. It will also provide techniques for accurate and improved diagnosis and for the presymptomatic screening of 'at risk' individuals within families and populations. An understanding of the genetic factors involved in multifactorial conditions, such as ischaemic heart disease and diabetes, will result in the development ofpersonalized prevention, tailored drug treatment and eventually 'cure.' The clinical geneticist's primary function will continue to be the provision of diagnosis and counselling of families with genetic and partly genetic disorders. They will have the facilities to make accurate diagnoses and to screen family relatives more efficiently for the disease causing gene mutations. It will be possible to make accurate assessment of risk and to provide more detailed information to enable patients and their relatives to make informed decisions. As many clinical disciplines embrace molecular medicine, the clinical geneticist will be a member in multi-discipline teams managing patients with single gene defects and complex disorders Clinicians will have direct access to analysis of gene expression using DNA micro-array technology. This will enable the simultaneous analysis of a thousands of unique DNA fragments, each fragment able to detect mRNA expressed from its corresponding gene. Micro-arrays have huge potential for many different fields in medicine, particularly in gene expression pattern recognition which characterizes disease states.' Gene expression profiling will not only be useful for haematological diseases and cancers, but also in unravelling the molecular aetiology of learning disability, skeletal dysplasias and 'dysmorphic' syndromes. Chromosomal analysis (cytogenetics) remains the main diagnostic test for learning disability, genetic syndromes and for reproductive loss and infertility. Currently, chromosomal abnormalities are diagnosed by conventional G-or R-banding methods but new techniques based on DNA hybridisation (FISH), spectral karyotyping (SKY) and spectral colour banding (SCAN) will enhance the ability of clinical cytogenetic laboratories to detect subtle genomic changes.2 The development of whole genome matrix-comparative genomic hybridisation is likely to achieve a …