Identical twins aren’t, exac tly

Identical twins don’t always have identical genetics, a University of Copenhagen study has found, which could explain why one might have autism but the other does not. Physical or behavioural differences are usually attributed to environmental factors, but during early embryonic development, mutations may create a developmental disorder. The study sequenced the genomes of 387 pairs of identical twins and their families, and found 5.2 early- developmental mutations, on average, and that in 15 per cent of identical twin pairs, one twin carries a high number of these mutations.