The Surprising Variability of Mitochondrial DNA

Researchers led by Johns Hopkins' Nickolas Papadopoulos found that different versions of the mitochondrial genome can be found in different organs in the same person. As they report in Nature, the researchers used next-gen DNA sequencing, and were able to find single-letter DNA changes that occur in as few as one in 10,000 mitochondria. And when the researchers tried to see if the variations were limited to cancer cells, what they found is that the mitochondrial DNA in healthy colon tissue can also vary. The implications for forensic science are clear — if mitochondrial DNA taken from a crime scene doesn't match a DNA sample taken from a suspect, that doesn't necessarily mean that the two samples aren't from the same person. And as for cancer detection, the researchers say that mutations specific to colon tumors can be found in tiny blood samples, and that those mutation signatures vanish after the tumor is removed.