Our genes are affected by the environment we live in and our lifestyles. All through certain chemical groups that can attach themselves to DNA. They determine the appearance of various diseases, including cancer, and also cause monozygotic twins to become increasingly different from each other over time.
Scientists have long believed that genes determine everything. Once we inherit them, the environment will not change them and we will stay with them until we die. A dozen years ago, however, it turned out that this is not the case — under the influence of environmental factors, genes can be switched on and off. The mechanisms responsible for this phenomenon were called epigenetic (the term means “above the genes”, the prefix epi comes from the Greek). Turning off a gene is another way to stop the synthesis of the protein it encodes. Usually, the activity (expression) of genes is inhibited by small chemical groups called methyl groups, which attach to specific DNA sites (mainly to cytosine), and the whole process is called methylation. Demethylation (removal of methyl groups) usually turns genes back on, which means that protein synthesis is triggered. There is no change in the composition of DNA here — all its “bricks” (nucleotides) remain the same.
From generation to generation
Epigenetic mechanisms were first observed in plants a dozen years ago. Some individuals of the common flax, a yellow-flowering weed, developed flowers made up not of two petals, as usual, but five, although the structure of their DNA was not altered at all. However, they differed in something special — they had a heavily methylated (and thus inactive) Lcyc gene. This was not the case in ordinary flax. In addition, it turned out that the trait of unusual petals was passed on to the next generation! Most of the progeny plants had the same five-petaled flowers and the same gene inactive due to methylation. Thus, the information was not deleted during reproduction.
Later, epigenetic phenomena were also found in animals. The discovery that the diet of rodents alters the functioning of their offspring’s genes was widely commented on, and these…