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A new study shows that while identical twins can look perfectly alike, it is not a perfect similarity. They are not clones of each other. Scientists at the University of Iceland analyzed the DNA from 387 pairs of identical twins - babies born from a single fertilized egg. The scientists compared the DNA with that of the twins' parents and children. The geneticists looked for mutations in the early stages of development. A mutation is a tiny change in the sequence of the DNA that can occur when a cell divides. This change causes a slight difference in the DNA replication process. A single, tiny change can create differences in height, intelligence, eye colour and even in susceptibility to disease.
The study shows that identical twins do not share totally identical DNA. In about 15 per cent of identical twin pairs, one twin carried a "substantial" number of mutations that the other did not share. The scientists say this difference is important as it sheds light on the "nature versus nurture" debate. This is whether human behaviour is determined by the environment, socialization and upbringing, or by a person's genes. The research shows that this tiny difference, and not environmental factors, could be the reason why one twin develops different behavioural characteristics or medical conditions. Professor Kari Stefansson said a genetic mutation may be the source of a given disease or trait.Comprehension questions
- What does the article say identical twins are not clones of?
- How many identical twins did scientists look at the DNA of?
- Whose DNA did scientists compare the twins' DNA to?
- What did the scientists look for?
- What might DNA mutations increase the susceptibility of?
- What does the DNA show identical twins do not share?
- What debate does the research shed light on?
- What might affect our behaviour besides socialization and environment?
- What might be the reason for differences in medical conditions?
- What does a professor say may be the source of a disease or trait?
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