a small fragment of a molecule (methyl group) of one carbon atom and three hydrogen atoms is attached to a specific place in the DNA sequence or to a histone protein with the participation of the enzyme methyltransferase. These “marks” rearrange the overall structure of the chromosome and thereby affect the activity of genes. Epigenetic markers, or markers, can have the opposite effect on gene activity. Some people discover a particular section of the chromosome, and the genetic information encoded in it becomes available for the synthesis of proteins. Others, on the contrary, close the chromosome, completely silencing the genes in this region.