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new study shows that while identical twins can look perfectly alike, it is not perfect similarity. They are not clones of each other. Scientists at University of Iceland analyzed the DNA from 387 pairs of identical twins - babies born from single fertilized egg. The scientists compared DNA with that of twins' parents and children. The geneticists looked for mutations in early stages of development. A mutation is tiny change in sequence of the DNA that can occur when cell divides. This change causes slight difference in the DNA replication process. single, tiny change can create differences in height, intelligence, eye colour and even in susceptibility to disease.

study shows that identical twins do not share totally identical DNA. In about 15 per cent of identical twin pairs, one twin carried "substantial" number of mutations that other did not share. The scientists say this difference is important as it sheds light on "nature versus nurture" debate. This is whether human behaviour is determined by environment, socialization and upbringing, or by person's genes. The research shows that this tiny difference, and not environmental factors, could be reason why one twin develops different behavioural characteristics or medical conditions. Professor Kari Stefansson said genetic mutation may be the source of given disease or trait.

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