Genotyping Markers

SNP markers are the latest generation of molecular markers that are found with high frequency in the genome of both animals and plants. With the development of SNP markers, it became possible to automate and increase the productivity of genotype analysis dozens of times.

Back in the early decades of the genetics’ development, it became clear that genetic markers can be useful in the analysis of complex traits. However, the low occurrence and a number of other shortcomings did not allow classical genetic markers, and subsequently protein markers, to enter widely into breeding practice. The latest generation of genetic markers (molecular, or DNA markers) is characterized by a higher frequency of occurrence in the genome and is based on universal, and therefore widely demanded and constantly developing methods of analysis. This became the key to the rapid development of genetics and breeding areas associated with the use of DNA markers.

With the development of molecular markers that make it possible to analyze genotypes at the level of the primary carrier of genetic information – DNA, the most diverse and most numerous class of markers has emerged today.

This is due to the fact that each separately taken nucleotide sequence is unique in its structure. The set of molecular genetic methods, called DNA fingerprinting, is most widely used in modern research to solve a variety of problems in various biological disciplines. In this regard, the need for a comparative classification of the currently existing molecular genetic markers seems relevant. Based on the published literature, data are provided on the proposed classifications of molecular markers.

The properties and distinctive features of genetic markers are given. It defines what a “good” genetic marker is, as well as the types, categories, variations and types of inheritance of molecular markers. The polymorphism detected using molecular markers is subdivided into polymorphism of the sequence itself (including nucleotide substitutions and insertion-deletions) and polymorphism of the number of tandem repeating sequences in repeated regions.

In addition, molecular markers can be classified into two variations: anonymous, i.e. those in which the nucleotide sequence is not known and its establishment is not required for the manifestation of a molecular marker (for example, RAPD, AFLP, RFLP), and announced (or determined), i.e. those in which the nucleotide sequence is known or detected during the analysis (for example, SNP, CAPS, STS). However, whatever the intended use of molecular markers, the choice of research method will also depend on the plant species being studied.