Molecular scanning methods of mutation detection.

Disruption of a single gene by mutation can have profound effects on a cultured cell or an entire organism. This review will not address the detection of known disease-causing mutations but rather the scanning methods that have evolved to define unknown mutations. It will be seen that the development of the polymerase chain reaction (PCR)’ (1, 2) has revolutionized the methods available for the detection of DNA mutations at the molecular level. Although specific human genes will be used as examples in this review, the techniques described have universal application to the study of any cloned gene. The varieties of mutations found in the human genome can range from the alteration of a single base to major rearrangements affecting large parts of or whole chromosomes. The existence of different types of mutation therefore means that diverse ap- proaches to mutation detection are required. Methods which detect large-scale alterations will be insensitive to point muta- tions, but on the other hand it is impractical to sequence vast stretches of DNA with no knowledge of where the mutation might occur. In some cases there is an observed predisposition to a particular kind of mutation affecting a gene, such as the dystro- phin and steroid sulfatase genes being prone to deletions (3-6) and the HPRT gene being prone to small mutations (7, 8). Mutation detection procedures can thus be tailored to the partic- ular gene of interest if such a predisposition exists or designed to detect virtually all types of mutation for a more universal ap- proach. Mutation Detection Methods