from the There's-dead-dead-and-there's-mostly-dead dept.
Huge swaths of our DNA library are made up of non-coding genes that were long regarded as "junk DNA". Recent findings, however, have shown these bits of DNA actually have many purposes in mammals.
Some help form the structure in our DNA molecules so they can be packaged neatly within our cell nuclei while others are involved in gene regulation. Now, researchers from the University of New South Wales in Australia have discovered another potential purpose for these non-coding instructions, within the genomes of marsupials.
Some of the gene sequences once considered "junk" are actually fragments of viruses left buried in our DNA from an infection in a long-forgotten ancestor.
Whenever a virus infects you, there's a chance it will leave behind a piece of itself within your DNA, and if this happens in an egg or sperm cell, it will then be passed on through the generations. These are known as endogenous viral elements (EVEs).
In humans, fragments of viral DNA make up around 8 percent of our genome. They can provide a record of viral infections through our evolutionary history, like genetic memory.
"These viral fragments have been retained for a reason," said paleovirologist Emma Harding. "Over millions of years of evolution, we would expect all DNA to change, however, these fossils are preserved and kept intact."
Emma F Harding, Grace JH Yan, Peter A White. Viral fossils in marsupial genomes: secret cellular guardians [open], Microbiology Australia (DOI: 10.1071/MA21036)