Identical twins are not so identical
Contrary to traditional beliefs, the genomes of identical (identical) twins are not 100% identical. This unexpected discovery is of great importance for the research of hereditary diseases and the development of new diagnostic methods.
There are cases when only one of identical twins develops, for example, Parkinson's disease. Until now, it was believed that the reason for this lies in the impact of environmental factors. An international team of researchers from the USA, the Netherlands and Sweden has demonstrated that genetic differences play a role in this.
The authors analyzed the genomes of 19 pairs of identical twins and found that they may differ in the number of copies of individual DNA fragments. Variations occur due to both the loss of genes (or DNA fragments) and the appearance of their additional copies.
A person receives one copy of each of the chromosomes from the mother and one from the father. As a result, everyone has two copies of the genome. In some cases, one of the chromosomes lacks a section, as a result of which a person has only one copy of the gene. Mutations are also possible, leading to the appearance of 3-4 or more copies of a certain DNA fragment. In most cases, variations in the number of copies of genes do not affect human health or development, but sometimes they increase the likelihood of developing diseases.
Studying changes in the number of copies of DNA fragments can shed light on the hereditary causes of diseases. For example, if one of the twins has a disease, and the second does not, the study of the region of their genomes, which has differences in the number of copies of a DNA fragment, may result in the discovery of the genetic basis of the disease.
Article by Carl E.G. Bruder et al. Phenotypically Concordant and Discordant Monozygotic Twins Display Different DNA Copy-Number-Variation Profiles published in the March issue of the American Journal of Human Genetics.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily
18.02.2008