Molecular biologists, scientists who study biology at the microscopic level, commonly call the DNA between genes “junk DNA.” As far as scientists know, these portions of the DNA do not code for any particular protein. In the past, more than 95% of DNA was called junk because it had no known function. However, scientists are beginning to find that this so-called junk DNA might not be junk after all.

After studying the DNA code in several different types of animals, scientists were very surprised to find that these noncoding DNA sequences seem to be very well preserved from species to species. In other words, there are large chunks of DNA that are exactly the same in humans and in other species like mice and rats. It is not just one small sequence, either. Scientists found 480 sections of DNA that were exactly the same in humans, mice, and rats. In addition, the scientists only looked at sections that were at least 200 bases long. This means that the possibility of the sequences being exactly the same just by chance is quite small. These same regions were also close matches in chickens, dogs, and fish.

Scientists call these sections of the DNA “super-conserved” regions because they seem to have remained unchanged over the 400 million years of evolution that separate rodents, chickens, and fish from humans. It is possible that these regions are essential for survival. That would explain why they have not changed over time. Scientists now suspect that, rather than being junk, the noncoding DNA may somehow regulate, or control, how the coding DNA functions.