'Cotton swabs can identify distant relatives'

A simple swab sample can accurately confirm relatedness between two individuals as distant as second cousins, a technique which could be used to identify disaster victims in mass floods, scientists say.

"Up till now, the accuracy of verifying pairwise blood relations between parents and children were 95 per cent and siblings around 72 per cent," said Keiji Tamaki from Kyoto University in Japan.

"With slightly more distant relatives like aunts and uncles it goes down to five per cent. As for cousins and second cousins, it was practically impossible. This new technique brings all of this to nearly 100 per cent," said Tamaki.
 

According to researchers, with more DNA datasets at hand, the method could be utilised to identify disaster victims in mass floods and tornadoes that destroy entire communities.

All the technique takes is a dab inside the cheek with a cotton swab. From these samples they compare 170 thousand single nucleotide polymorphisms (SNP), which are locations where the genetic code varies minutely from person to person.

Instead of simply comparing how each individual SNP matches, they also examine how many consecutive matches there are.

"Our inspiration for the project came from tsunami victims in the 2011 Great East Japan earthquake. Many tsunami victims passed away, and over 70 of them have yet to be identified even though five years have passed," said Chie Morimoto from Kyoto University.

DNA collected from personal belongings left at home - for example, toothbrushes the person used to use - are reliable material for personal identification, researchers said.

Tsunamis, however, wipe away entire communities, leaving forensic scientists with no direct clues.

In such instances, testing for blood relations is the only beacon of hope; but this also has its limitations, because it can only confirm blood relationships between first-degree relatives like children or siblings.

The findings were published in the journal PLOS ONE.