Single nucleotide substitutions (SNPs) account for the largest share of DNA polymorphism in virtually any organism, including humans, and have a significant impact on their life status. Detection of already known polymorphic nucleotides (SNP typing) is of great importance, which explains the extremely wide variety of existing methods for SNP analysis. One of the most widely used approaches is allele-specific PCR (AS-PCR) with primers characterized by differences in structure and the resulting ability to discriminate polymorphic nucleotides in DNA. AS-PCR is implemented in a variety of variants (about fifty), which are briefly considered in this review.

Due to the fact that single nucleotide substitutions account for the largest share of DNA polymorphism in almost any organisms and have a noticeable effect on their vital status, the detection of already known such polymorphic nucleotides is extremely important. This explains the huge variety of methods of such genotyping. Among the old approaches to the detection of polymorphic nucleotides, allele-specific hybridization with oligonucleotides stands out, which later received a new life in the form of fluorescently labeled probes. Also, such a method as PCR-RFLP, based on the cleavage of amplicons by suitable restriction endonucleases, whose sites contain polymorphic nucleotides or primers are designed in such a way that such sites arise during PCR, is not completely forgotten. The methods used relatively less frequently for detecting mutations in heteroduplexes using some chemical reagents, as well as using some endonucleases, are also briefly considered in this review.