DNA 'Cheaters': ‘Selfish’ introners drive genetic complexity and cross-species transfer, study finds

Hidden DNA 'Cheaters' Found Hopping Between Species, Say Scientists (Image: Canva)

Sometimes, the secrets in our DNA are not helpful. They lie low, copy themselves quietly, and wait to move again. These genetic stowaways, once thought harmless, have now revealed a surprising skill — jumping between species.

A new study from the University of California, Santa Cruz, confirms that a type of genetic element known as “introners” helps spread introns within and across species. The study, published in Proceedings of the National Academy of Sciences, found eight confirmed cases of these introners jumping between unrelated species. This marks the first solid proof of such transfers through a process called horizontal gene transfer.

DNA holds the code for building life, but not all of it is useful. Some parts behave more like parasites, sticking around simply to ensure their own survival. These “selfish” DNA elements often need to be removed before a cell can build proteins — the body’s basic tools. While this process supports life’s complexity, it can also lead to serious illnesses like cancer.

Researchers studied how introners make copies and hide themselves inside a species' DNA. Senior author Russ Corbett-Detig, a professor of biomolecular engineering at the Baskin School of Engineering, said introners help shape genome complexity — but not because of natural selection. “A few may ultimately benefit the host,” he said, “but most are just cheaters that found a really good way to hide in the genome.”

Introners belong to a group of “jumping genes,” also known as transposable elements. These genes can move around within a genome and carry introns with them. The study shows that introners are one of the main ways new introns appear in DNA.

Previous studies hinted at this theory, but new methods allowed researchers to confirm it. The team analysed DNA from thousands of species — something only recently possible thanks to large-scale projects like the Earth BioGenome Project and the Sanger Tree of Life. These global efforts are helping scientists uncover deep patterns across the tree of life.

By tracing introners across species, researchers are learning more about how DNA evolves. The findings offer a clearer view of how genetic elements behave and how life adapts — even with a few “cheaters” along for the ride.