Polymerase chain reaction and other methods to detect hot-spot and multiple gene mutations.

Gene mutations responsible for main genetic diseases as Duchenne/Becker muscular dystrophy or cystic fibrosis, and involved in more important diseases like cancer or cardiac diseases have been identified. Direct DNA tests can now be performed for these disorders. However, despite the knowledge of the exact alteration of the DNA sequence in these diseases, incorporating DNA analysis into large screening programs has been hindered by technical difficulties since each different mutation requires a different probe to be detected. To overcome these problems the polymerase chain reaction technique (PCR) has been proposed. Multiplex PCR procedure is possible and consists of simultaneously amplifying several separate DNA sequences (the upper limit of the number of multiplex reactions that can be executed at one time is not known; eight or nine separate DNA sequences amplified have already been described). Another approach is to directly sequence the gene mutations generally concentrated in 'hot-spot' regions. This way it is possible to identify numerous mutations using only one micro-sequencing reaction (50-100 nucleotides). New generations of very sophisticated systems like capillary electrophoresis or non-isotopic, but very sensitive, microsequencing systems should allow in a near future to withdraw the use of PCR for this purpose.