To help identify the Vietnam-era remains in the Tomb of the Unknowns, scientists will analyze genetic material – but not the kind of DNA most people think about.

That DNA is in the nucleus of the cell, and each cell contains two copies. Researchers will in stead focus on mitochondrial DNA, or mtDNA, found outside the nucleus. Each cell has thousands of copies of mtDNA.

That’s important because DNA breaks down in a harsh environment. With a lot more copies of mtDNA than nucleus DNA to begin with, there’s a much better chance that some mtDNA will still be around to analyze now.

“The conditions in southeast Asia are not very good for DNA,” said Mitchell Holland, who over sees the military laboratory where the analysis will be done. “It’s hot, humid, and the soils are somewhat acidic. And because of that, mtDNA is really the only available method.”

Even so, the Pentagon cautions that it’s not certain the bones will be identified by the mtDNA analysis.

DNA contains long sequences of four chemicals, abbreviated as A, C, G or T. The sequence of these chemical links – like CAAACTGGT and so on – contains genetic information. To analyze mtDNA, researchers look at the sequences in two places with a total of about 600 chemical links.

Two unrelated people generally have much different sequences, but a mother and son will show the same. Mothers – not fathers – pass mtDNA on to children.

So Holland’s lab, the Armed Forces DNA Identification Laboratory in Rockville, Md., is looking for matches between the sequences in the Vietnam-era remains and those in samples from the families.

By itself, a match would not mean an ironclad identification. But less than 1 percent of personnel still missing from the Vietnam war would be expected to match a given mtDNA pattern. So, Holland said, it’s highly unlikely that a match would be pure coincidence. The AFDIL has conducted more than 300 mitochondrial DNA testings since 1991. Their success rate is 85 percent and getting better with each new technological improvement that comes along.

“It’s an evolutionary process whose technology is improving all the time,” Deputy Program Manager James Canik said. “With mitochondrial DNA, it is very, very labor intensive. And there are certain cost restraints.”

Those cost restraints are considerable when compared to the cost of nuclear DNA samplings, which can run from $10 to $100 a sample. MtDNA is about $4,000.

“We can’t ever lose sight of the families in the process. Emotions run very high. It can be years and years since they lost their son or daughter but people never forget,” says Canik.

Information from the Manchester (N.H.) Union leader was used to supplement this report.