Japanese authorities who are still trying to identify the remains of victims of the 2011 Great East Japan Earthquake and tsunami say they are having greater success testing mitochondrial DNA (mtDNA) compared to conventional testing methods.
Since last year, seven bodies whose identifications were requested by the Miyagi prefectural police were identified by the National Research Institute of Police Science in Kashiwa, Chiba Prefecture, using the technique. The research institute is affiliated with the National Police Agency.
Mitochondrial DNA is passed down from mother to child unchanged, making it possible to identify an individual with near certainty and match them with relatives. Normal DNA testing becomes increasingly inefficient the more time has passed since cell death.
Emi Sato, 42, a nursery school teacher in the Shizugawa district of Minami-Sanriku, Miyagi Prefecture, whose uncle’s body was identified using the mtDNA identification method in October, praised the procedure.
“I am relieved now that my uncle has finally returned to me," she said. "I appreciate the professional analysis used to identify him.”
The institute’s Fourth Biology Section tested DNA samples provided by the Miyagi prefectural police by dissolving them in a special chemical to extract a victim’s mitochondria from cells.
The researchers then take about a week to examine the DNA and sequence it.
Regular DNA testing analyzes DNA contained within the nucleus of a cell. But the DNA, which is vulnerable to ultraviolet radiation and bacteria, is often too degraded in bodies that have drifted at sea for some time to be of use.
Mitochondrion, on the other hand, is found in large numbers. Anywhere from dozens to tens of thousands of mitochondria are present in a single cell. That raises the chances of extracting usable DNA, according to the institution.
The institute started conducting mtDNA identification in 1996. It now receives about 60 requests for the procedure annually, a three-fold increase compared to pre-3/11 levels.
It takes researchers up to a month to complete the examination of a sample if it is in poor condition.
“We hope to review our tools and drugs to enable quicker and more accurate identification and better prepare for the next disaster,” said Kazumasa Sekiguchi, head of the Fourth Biology Section.
The remains of 99 victims of the disaster in Iwate, Miyagi, and Fukushima prefectures, as of Feb. 20, are still unidentified.
Friday 21 February 2014
http://ajw.asahi.com/article/behind_news/social_affairs/AJ201402210065
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