Transposons or 'jumping genes', which create genomic instability and are implicated in cancer and other diseases, make up roughly half of the human genome, geneticists have revealed.
"Now it looks like every person might have a new insertion somewhere," says senior author Scott Devine, associate professor of medicine at the University of Maryland School of Medicine's Institute for Genome Sciences.
Transposons are like small self-replicating sequences that transfer themselves from one generation to another. But the scientists faced the overwhelming problem of finding a new insertion within three billion base pairs.
Their study indicated transposons are jumping in tumours and are generating a new kind of genomic instability. They are already known to interrupt genes and cause human diseases, including neurofibromatosis, hemophilia and breast cancer.
Scientists believe a process called methylation, which silences genes during differentiation also shuts off transposons' ability to jump. Analysing the patterns of mutations in the lung tumours suggested that during tumour formation, modified methylation patterns may be allowing transposons to re-awaken, Devine says.
The results are published in the June 25, 2010 issue of Cell.