The diagnosis and treatment of human disease is one area in which genetic manipulation is beginning to have a considerable effect. As outlined in Chapter 10, many therapeutic proteins are now made by recombinant DNA methods, and the number available is increasing steadily. Thus the treatment of conditions by recombinant-derived products is already well established. In this chapter we will look at how the techniques of gene manipulation impact more directly on medical diagnosis and treatment, and will also examine the use of rDNA technology in forensic science. Progress in both of these areas is of course closely linked to our increasing knowledge of the human genome, and thus many new developments in medical and forensic applications will appear as we decipher the genome.

Diagnosis and characterisation of medical conditions

Genetically based diseases (often called simply ‘genetic diseases’) represent one of the most important classes of disease, particularly in children. A disorder present at birth is termed a congenital abnormality, and around 5% of newborn babies will suffer from a serious medical problem of this type. In most of these cases there will be a significant genetic component in the aetiology (cause) of the disease state. It is estimated that about a third of primary admissions to paediatric hospitals are due to genetically based problems, whilst some 70% of cases presenting more than once are due to genetic defects. In addition to genetic problems appearing at birth or in childhood, it seems that a large proportion of diseases presenting in later life also have a genetic cause or predisposition.