January 12, 2022 feature
by John Hewitt , Medical Xpress
Around half of the genome is made up of transposable elements or 'jumping genes' that derive from ancient viral integrations. They persist in various states of decay like an old fashioned 'pull your own' junkyard where parts from old scrapped vehicles can be harvested and repurposed. While most of these sequences really are junk, treasures can be found in their ore.
Retrotransposons that are specific to mammals; the common LINE-1 (L1) element, for example, comprises a class of transposons that salt our genomes to the tune of a couple hundred-thousand genetic mini-islands. That's about 20% of our total sequence. Of the few thousand L1s that are still mostly full-length, only about 100 or so have maintained their full coding potential, i.e., are still able to move around the genome by retrotransposition. This involves a copy-and-paste mechanism using a reverse transcriptase specified in their second and final open reading frame, commonly designated as ORF2.