More accurately called DNA profiling, this technique was first used to identify criminals. Now it is an important tool in forensic archaeology used to identify individuals, such as the Romanovs, and also to gain information about people in the past.

DNA is the genetic material found in every cell of every living thing. The DNA molecule is a double helix – it looks like a ladder that has been twisted into a spiral. The uprights are the same for everyone, but the sequence of the rungs is unique for each person, apart from identical twins.

Forensic scientists use enzymes to cut the DNA into short pieces, and these fragments vary in length, depending on the individual's genetic code. The fragments are separated according to their size, using an electric current, then they are labelled with a radioactive substance. An X-ray of the labelled fragments produces a 'DNA fingerprint' that looks rather like a bar code.

The DNA from the cell nucleus is fragile and can be difficult to read if the samples come from very old bodies. But another, more stable, form of DNA is found in the mitochondria – the structures that produce the cell's energy. Mitochondrial DNA is harder to test and can only indicate relationships through the maternal line, but it provides important information about archaeological finds.

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DNA fingerprinting
(Science Photo Library)

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