Researchers from the US found that those who have the genetic mutation are identified as having the letter A, short for the biological molecule adenine, replaced with the letter G, which stands for guanine.
This single variant in the genetic code raises the risk of developing certain types of glioma brain tumours by six times, the Daily Mail reported.
"Understanding how this variant causes people to get these less aggressive, but still lethal, tumours will be extremely important. It may eventually lead to methods to reverse the course of these tumours or possibly to prevent their formation," Professor Margaret Wrensch, one of the scientists from the University of California at San Francisco, said.
"Based on our findings, we are already starting to think about clinical tests that can tell patients with abnormal brain scans what kind of tumour they have, just by testing their blood," co-author Dr Robert Jenkins, from the Mayo Clinic in Rochester, Minnesota, was quoted by the paper as saying.
The DNA region studied has been conserved through evolution as far back as the duck-billed platypus, a primitive egg-laying mammal, said the scientists.
The letter-swap change was found in a particular region of chromosome eight, one of the 23 pairs of protein-wrapped DNA packages in every normal cell that contain the genes.
Scientists believe this DNA region may provide the instructions for making a microRNA, a tiny molecule that controls gene activity.
"The altered microRNA might target tumour suppressor genes, it might activate a cancer gene, it might be involved in regulating the stability of the genome (genetic code), or there might be something else going on altogether," Jenkins said.
The study was published in the journal Nature Genetics.
