Between the genes – U of T researchers make sense of the “dark matter”
May 20, 2010
TORONTO, ON – A new discovery by University of Toronto scientists has uncovered the secrets behind what many in the field of molecular genetics have referred to as the mysterious”dark matter” of DNA.
This “dark matter” refers to what once thought of as nothing more than “junk DNA,” located in regions outside of actual genes. When it was discovered that genetic signals, or transcripts, were coming from this area, many believed that there was a whole new mystery to solve, and that there was much more going on than originally expected.
However, a new study, led by Postdoctoral Fellow Harm van Bakel and Prof. Timothy Hughes from the Department of Molecular Genetics, has shown that most of these signals are likely to be by-products of signals from already-known genes. Most of the others, the research indicates, are more background noise than meaningful signals.
“The mystery is solved,” says van Bakel. “Almost all of the ‘dark matter’ has very little significance after all.”
Part of the mystery came from the methodology. Many reports of dark matter signals used “tiling arrays,” which the researchers determined was creating too many false positives. By using a method of sequencing large numbers of RNA transcripts, a technique that has only recently been available for a few years, they were able to determine that unexplained dark matter only accounted for 2 per cent of the total genetic signaling, much less than originally believed. Of that 2 per cent, most are very close to one or another end of a gene, indicating that they are likely copies of signals expressed by the gene itself.
“Given the mystery and novelty in the field of genetics, it’s important to know where to focus our search,” says van Bakel. “Up until now, we had no way of knowing if we were missing out on some key genetic information contained in this dark matter. This discovery allows us to zero in on what is really important.”
“The dark matter transcripts are not signals emerging from a hidden universe within the genome,” says van Bakel. “It’s more like noise emitted by a busy machine.”
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