Since Crick and Watson’s historic discovery of DNA, our investigation into coding DNA has gone a long way towards unravelling the key to life—but coding DNA only makes up just a few percent of the human genome. The rest is termed “Junk DNA” or “Non-coding DNA” because it doesn’t appear to have any function. However, new research suggests that this Junk DNA might actually play an important role in evolutionary history. Huge “ultraconserved” sections of it have remained the same for millions of years and are identical in many organisms—when you hear that humans and chimps share 98% of DNA, it’s mostly due to this. Increasing evidence suggests that Junk DNA influences coding DNA by acting as a kind of genetic “switch” in gene regulation, and it may also play a role in inheritance, but our knowledge is incomplete. If Junk DNA were really junk, then its sequence of “syllables” should be completely random, but it’s not random—leading scientists to believe it contains some kind of coded information. It’s been suggested that specific repetitive patterns are associated with susceptibility to cancer and other diseases, so understanding Junk DNA might be the key to understanding, diagnosing and curing disease.
Ancient Viral DNA in the Human Genome
Traces of ancient viruses, which infected our ancestors millions of years ago, are more widespread throughout our modern-day genomes than was previously thought.
The new research sheds light on the origins of a large proportion of our genetic material, much of which is still not understood. Only about 1.5% of human genes code for a useful protein product, that we’ve discovered; half of the rest is labeled “junk DNA” - although new research indicates it has a variety of purposes - while the other half was introduced by viruses or parasites, like the ancient ones studied here.
The senior author on the study (published in the Proceedings of National Academy of Sciences), Dr. Robert Belshaw from Oxford University’s Zoology Department, said: “This is the story of an epidemic within every animal’s genome, a story which has been going on for 100 million years and which continues today.
“Much of the dark matter in our genome plays by its own rules, in the same way as an epidemic of an infectious disease but operating over millions of years.
Learning the rules of this ancient game will help us understand their role in health and disease.”
Not only do these viruses exist within our genomes, but some of are even helpful, Dr. Belshaw insists. Protein syncytin, for example - derived from a virus - helps develop the human placenta.
The study believes that unlocking the secrets of these viruses is essential to understanding the full complexity of the human genome.
Image: SEM image of Influenza A virus.