DNA Genotyping

Over the years, many different SNP typing techniques have emerged that are based on different allele discrimination techniques. To understand each of the technologies, it is necessary to separate the allele discrimination response and the detection method. The products of the allele discrimination reaction can be detected by more than one method, and the same methods can be used to detect the products obtained using other reactions and samples.

Most SNP genotyping methods can be grouped into four groups based on their molecular mechanism of action:

  • allele specific hybridization;
  • primer extension;
  • oligonucleotide ligation;
  • restriction endonuclease analysis.

There are several methods for identifying products and their analysis for each group of the above reactions (fluorescence, luminescence, etc.). There are also two categories of reactions depending on their type: homogeneous reactions, i.e. reactions in solutions and reactions that take place on a solid surface, such as adsorption on a glass surface. Homogeneous reactions are more conducive to the automation of the allele discrimination process, because they do not require a separation and / or purification step after them. However, the main obstacle is the limited ability for multiplex analysis, whereas reactions on solid surfaces have more possibilities for multiplex analysis, although they require additional manipulations.

SNP genotyping technologies are being developed very quickly, and as a result, today there are a large number of SNP genotyping protocols. There are many factors to consider before identifying the best and most useful method for judicial practice. An important limiting factor of all methods can be recognized as the need for a large amount of material for the study of each individual genotype.

Another important factor is the research of solutions. It is sometimes difficult to thoroughly investigate the structure of some mixtures using the markers offered in the methods. Currently, the most popular method is minisequencing, especially the SNaPshot method. It is assumed that each of the techniques will take its place in forensic laboratories and it will be possible to combine and joint use of different techniques in determining, for example, the Y chromosome. It is also planned to create a database for all SNPs.