Looking at DNA differences
Between any two people, on average one DNA base pair in every thousand varies - but this variation is not spread evenly throughout your DNA. Only 3 per cent of your DNA is part of a gene, while most of the remaining 97 per cent has no known job. This 'non-coding' DNA is far more variable than the DNA that makes up genes. Scientists can look at these DNA differences using several techniques, the best known of which is DNA fingerprinting.