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Y, it?s a match

What?s in a surname? Plenty, say researchers from the University of Leicester, Britain, writes Prakash Chandra.

india Updated: Mar 06, 2006 01:34 IST
SCI-FILES | Prakash Chandra
SCI-FILES | Prakash Chandra

What’s in a surname? Plenty, say researchers from the University of Leicester, Britain, who have developed a technique to use DNA retrieved from crime scenes to predict the surnames of suspects. The method is based on similarities in the Y chromosome — genetic material found exclusively in males — that the son inherits from his father, just like the surname. Sharing a surname, it appears, also raises the likelihood of sharing the same type of Y chromosome: rarer the surname, stronger the link. This means a criminal could be identified from a database of surnames and their chromosome profiles. Police need to just shortlist names predicted by the Y chromosome and see if they appear in the pool of suspects. Profiling a DNA sample to ensure it matches the crime scene sample would then provide irrefutable proof.

‘DNA fingerprints’ are a record of our genetic makeup. The DNA molecules we inherit from our parents determine our individual characteristics, from foot size to eye colour. Except for identical twins, everybody’s DNA is different — a uniqueness that makes DNA such a valuable identification tool. ‘DNA fingerprinting’ uses certain chemicals to amplify DNA samples — sometimes a thousandth the size of a grain of salt — to reveal an individual’s genetic identity. The data is transcribed into a ‘bar code’ that computers compare with other samples with far more precision and speed than the best conventional fingerprint expert. Skin cells, blood, nasal mucus, or even a dab of saliva on stamps pasted on hate-mail, all help track down an elusive killer. Even fingerprints too smudged for ordinary identification  yield enough DNA for a ‘fingerprint’ to be made.

Forensic scientists even recover DNA transferred by a mere handshake, from objects that people touched for as little as five seconds a year ago!

Basic DNA fingerprinting methods, however, take weeks of painstaking work, and on-the-spot DNA analysis has always been considered science fiction. But researchers at the Institute for Nanotechnology at Northwestern University, Illinois, have now invented a way to instantaneously analyse DNA by detecting faint electrical signals from sequences of DNA molecules. Microscopic gold-plated electrodes — nanoprobes — emit an electrical charge when a piece of DNA being tested matches a standard sequence for, say, anthrax genes or human mutations in a disease gene. This could enable doctors to analyse patients for genetic disorders or inherited intolerance to certain drugs. Thousands of times more accurate than current techniques, this could be used anywhere from crime scenes to a doctor’s surgery.

It may not be long before it’s built into hand-held devices, making genetic screening at airports and security establishments a cinch.

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