DNA 'identichip' gives a detailed picture of a suspect

IMAGINE you are trying to solve a burglary, and your sole lead is a cigarette butt. It has enough DNA on it to check against the national DNA database, but this throws up no matches. Running the DNA through machines capable of identifying physical characteristics could help - only there is not enough DNA to deduce more than two traits.

A new all-in-one chip that can identify multiple traits should help. The Identitas v1 Forensic Chip allows investigators to home in on someone's gender, eye colour and hair colour, as well as ancestry - all based on a small sample of DNA such as that from saliva on a cigarette butt.

Developed by VisiGen, a consortium of universities and law enforcement agencies, the chip is the first to provide data on all these traits simultaneously. Other devices can determine at most two at a time - usually eye and hair colour.

The new chip contains hundreds of thousands of short sequences of DNA that bind to different single nucleotide polymorphisms (SNPs) - single letter variations in the genetic sequence - in the DNA sample. SNPs are indicative of physical traits, so once we know which SNPs are present in the sample, software can be used to compute likely appearance and ancestry.

The VisiGen team tested the chip on more than 3000 DNA samples collected around the world, and found that it was 99 per cent accurate at predicting gender. The chip also predicted European or East Asian ancestry with an accuracy of 97 per cent, and African ancestry in 88 per cent of cases. However, it was only 63 per cent accurate at predicting blond hair (International Journal of Legal Medicine, doi.org/j5k).

The tool is not accurate enough to secure convictions in court, but team member Aruna Bansal of New York biotech firm Identitas envisages it being useful in focusing investigations or corroborating eyewitness reports, as well as in identifying disaster victims. "It provides you with a starting point," she says. The current chip is ready to be launched and the team is now working towards a chip that can determine even more traits.

Erin Murphy, a professor of law at New York University, is concerned that this technology may encourage "police dragnets", in which anyone matching a profile created with such chips could be questioned. But VisiGen team member Manfred Kayser of the Erasmus Medical Center in Rotterdam, the Netherlands, counters that the authorities "already use all types of information for investigative purposes". With the chip, the only difference is that they will be looking at DNA-derived traits.

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