CNN Identical twins may not be quite as identical as we thought; researchers in Iceland have discovered genetic differences that begin at the early stages of embryonic development. Twin studies have long been used to examine the effects of nature versus nurture. Scientists have long used the study of identical twins to examine the effects of nature versus nurture, as the accepted view has been that, because they share the same genes, any physical or behavioral differences between such siblings must be down to outside influences. However, this may not be the case, suggested the new research, published Thursday in the journal Nature Genetics.
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B arbara Oliver has had an intriguing relationship with her identical twin sister, Christine, over the decades. Throughout their childhoods, they were effectively treated as two versions of the one person: they were dressed in exactly the same manner and were given the same hairstyles. But when Barbara and Christine reached adolescence in the 60s, the pattern changed. The girls could choose their own clothes and adopted very different fashions. Christine had longer dresses and jackets," says Barbara. At the same time, differences in their personalities became more apparent.
Unique and Unusual Types of Twins
Research published on January 7 in the journal Nature Genetics shows that identical twins differ by an average of 5. The study of pairs of identical twins and two sets of identical triplets found that only 38 were genetically identical, Tina Hesman Saey reports for Science News. Most had just a few points of genetic mismatch, but 39 had more than differences in their DNA. The findings could impact future studies of the ways that the environment affects disease and human development.
Doctors have documented what they say is only the world's second known case of "semi-identical" twins. The boy and the girl, now four, from Brisbane, in Australia, are identical on their mother's side. But they share only a proportion of their father's DNA - placing them, genetically, somewhere between fraternal and identical twins. Prof Nicholas Fisk, who led the team that cared for the mother and twins at the Royal Brisbane and Women's Hospital in , said the discovery was made through a routine pregnancy scan. Identical, or monozygotic, twins occur when a single egg, fertilised by a single sperm, divides and makes two babies.