News Archive 10 September 2009

25th anniversary of the DNA fingerprint
10 September 2009

Today, the DNA fingerprint is 25 years old. Wellcome Images holds a photo of the original autoradiograph, discovered by Professor Sir Alec Jeffreys in his lab at Leicester University, where he still works today.

This image, acquired in 2005, represents a greatly important discovery for the field of forensic science. Thanks to later technological improvements, a microscopic sample of DNA can now be analysed to produce a DNA profile sufficient to convict a criminal.

DNA profiling uses the very small variations in DNA to distinguish or relate individuals. 99.9 per cent of our DNA is the same as everyone else's, but in the remaining 0.1 per cent are repeated sequences which are very similar in related people, but very unlikely to be similar in unrelated people. Apart from identical twins, it is widely agreed that no two people have the same DNA fingerprint. As such a fingerprint from a sample at a crime scene can be compared to a suspect's, and if there is a match, the evidence against them is very strong.

The first DNA fingerprint shows 11 lanes of DNA. The last eight are from various animal species, showing a lot of variation. The first three are from a woman, her father, and her mother. The pattern of dark and light lines, representing the repeated short stretches of DNA called minisattelites. The patterns are very similar, which indicates the close relation of the three samples.

Professor Jeffreys's discovery has not only benefited forensic science, but has enabled the tracking of historical migration of groups, and revealed family ties for children whose parentage is unknown.