Identical twins don 't always have identical DNA, new study finds.
Identical twins differ by 5.2 genetic changes on average, according to a new Jan. 7 Report in Nature Genetics , as indicated by Scientific News . This study runs counter to the belief that identical twins are genetically identical, which has often been the basis of the idea that differences in health between twins are a result of their environment. This new study shows that genetics may have more to do with it than previously thought. " Imagine having identical twins raised separately "said the CEO and founder of DeCode Genetics, and study co-author, Kari Stefansson, CNN . " If either of them has developed autism, the classic interpretation is that it is. is due to environmental factors. But our work shows that before concluding that it is caused by the environment, you need to sequence the genome of the twins to find out what might matter for autism. "
Stefansson said this
Identical twins, also known as monozygotic twins because they originate from a single fertilized egg, as Science News notes, are often studied to determine the origin of traits , diseases or specific conditions, whether the result of genetics or thesult of their environment. This study included 381 pairs of identical twins and determined that 38 of the pairs had identical genetics, but most of the pairs had DNA differences that appeared very early in their development. Thirty-nine of the pairs had over 100 changes between twins and the study suggests that these DNA differences occur when the embryo separates into two at the start of development or shortly after the embryo separates. This suggests that this
Some twins occur when a single cell or a small group of cells separate from the embryo, Science News notes, and it is the number of cells a twin is made from that can determine the differences genetics between him andt his other twin. The more uneven pisions of the embryo that occur, the more genetic differences between the twins.
"This is an extraordinary, exciting and insightful effort to identify the first cellular mechanisms that explain the genetic differences between MZ (monozygotic) twins, " California State University, Fullerton , psychology professor Nancy Segal, told CNN. "It is well known that MZ co-twins do not bear a perfect resemblance and that some differences may reflect genetic differences. The present study offers new information as to the source of the differences in MZ co-twins. < output class = "article-video-container "> According to Segal, the study shows that "some twin models underestimate the genetic effects and require revision.
For more twins, check out our list of the best movie twins of all time , and if you're looking for more DNA science, read this article on how New study reveals that most Vikings weren't blond or blue-eyed . Wesley LeBlanc is a freelance news writer and guide maker for hfrance. You can follow him at Twitter @LeBlancWes . 
