EN
Epigenetic modifications, apart from affecting gene expression, play an important role in the chromatin structure stabilization, embryonic development and the genomic imprinting. Recent studies have shown that they also play a vital role in other biological processes, including silencing of the expression and mobility of transposable elements and resistance to viral infections by blocking the expression of viral genes. The stability of the genome and the expression of genes in normal cells are strongly dependent on the DNA methylation pattern, which is visibly disturbed in tumor cells. These alterations may be a consequence of the attachment of methyl groups to cytosines in unmethylated DNA sequences, resulting in an increase in the degree of methylation or can be a result of demethylation, i.e. a reduction in the level of DNA methylation. Currently, many techniques are available to determine the level of methylcytosine in DNA, both at the level of single genes and the whole genome. However, each method has its advantages and disadvantages, not being universal in relation to the type of research material and the purpose of planned analyses.