RARE snippets of genetic material locked inside fragments of bone and teeth can help identify people who die at war or sea, even when little remains of their bodies. But often there simply isn’t enough DNA to be sure. A new technique, recently used to identify the Titanic’s “unknown child”, could make it easier for bereaved families to get a positive ID.
To extract DNA, researchers mix ground-up fragments of tooth or bone with a solution containing a chemical called EDTA, which removes calcium from bone. Mike Coble of the US Armed Forces DNA Identification Laboratory in Rockville, Maryland, and his colleages increased the concentration of EDTA and added an enzyme called pro-K, which breaks down the crystallised clumps of protein that lock DNA away in bone (Forensic Science International: Genetics, in press). The net effect, says Coble, was to “liberate” more DNA, increasing the chances of identifying remains.
In the case of the unidentified child who died in the Titanic disaster, the new technique enabled Ryan Parr of Lakehead University in Ontario, Canada, to say that the remains were most probably not those of Eino Panula – as initially thought – but another child, Sidney Goodwin.
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However, as with most identifications, Goodwin’s relies on DNA from mitochondria, because it is more abundant than DNA from cell nuclei. Nickolas Papadopoulos of the Howard Hughes Medical Institute in Baltimore, Maryland, cautions that excluding someone on the basis of mitochondrial DNA (mtDNA) alone might be a mistake.
In a study published this week, his team shows that mtDNA can vary within different tissues of the same individual. Previously it had been assumed that mtDNA was the same in every cell (Nature, ). “It doesn’t mean that you can’t use mtDNA, it just means that you have to be careful about who you exclude,” says Papadopoulos.
Other evidence, like shoes found with the body, suggests that the child was indeed Goodwin. In future, though, Coble’s technique should reduce the reliance on mitochondrial matching, as it will often be possible to extract sufficient amounts of nuclear DNA from badly damaged remains.
“In battlefield remains, often all you end up with is bone and teeth,” says Louis Finelli, director of the US Department of Defense DNA Registry. “In most cases we weren’t getting anything but mtDNA, but this technique means we can use more of the bone and as a result pull out more DNA.”
That should come as welcome news to the thousands of families still waiting to find out about loved ones following conflicts like the Vietnam and second world wars. “For them, the wounds are as fresh as if it had occurred yesterday,” says Finelli.
“The technique should be welcome news for families waiting to find out about deceased relatives”
