- 'Long terminal repeats' (LTRs) are a form of 'junk DNA' -- genetic material that has accumulated in the human genome over millions of years. Although LTRs originate from viruses and are potentially harmful, they are usually made inactive when embryos are developing in the womb.
If this process of inactivation doesn't work, then the LTRs could activate cancer genes, a possibility that was suggested in previous animal studies. This latest research has now demonstrated for the first time that these 'rogue' active LTRs can drive the growth of cancer in humans.
Phenotypic expression in action?