In rare cases of the classic manifestation of a monogenic disease and/or the existence of major mutations in the population (VHL syndrome with a candidate gene of three short exons, BRCA1/2 mutations in Ashkenazi Jews and Eastern Slavs, and an MSI test for Lynch syndrome), analysis is possible, at least in the first stage, using classical methods, such as PCR, Sanger sequencing, and MLPA. This evidence concerns the gene BRCA1 and Lynch syndrome.