Breakthrough Study Overturns Theory of ‘Junk DNA’
The international Encode project has found that about a fifth of the human genome regulates the 2% that makes proteins
By Alok Jha, science correspondent, The Guardian – September 5, 2012
Long stretches of DNA previously dismissed as “junk” are in fact crucial to the way our genome works, an international team of researchers said on Wednesday.
It is the most significant shift in scientists’ understanding of the way our DNA operates since the sequencing of the human genome in 2000, when it was discovered that our bodies are built and controlled by far fewer genes than expected. Now the next generation of geneticists have updated that picture.
The results of the international Encode project will have a huge impact for geneticists trying to work out how genes operate. The findings will also provide new leads for scientists looking for treatments for conditions such as heart disease, diabetes and Crohn’s disease that have their roots partly in glitches in the DNA. Until now, the focus had largely been on looking for errors within genes themselves, but the Encode research will help guide the hunt for problem areas that lie elsewhere in our DNA sequence.
Dr Ewan Birney, of the European Bioinformatics Institute near Cambridge, one of the principal investigators in the Encode project, said: “In 2000, we published the draft human genome and, in 2003, we published the finished human genome and we always knew that was going to be a starting point. We always knew that protein-coding genes were not the whole story.”
For years, the vast stretches of DNA between our 20,000 or so protein-coding genes – more than 98% of the genetic sequence inside each of our cells – was written off as “junk” DNA. Already falling out of favour in recent years, this concept will now, with Encode’s work, be consigned to the history books.
Encode is the largest single update to the data from the human genome since its final draft was published in 2003 and the first systematic attempt to work out what the DNA outside protein-coding genes does. The researchers found that it is far from useless: within these regions they have identified more than 10,000 new “genes” that code for components that control how the more familiar protein-coding genes work.
Up to 18% of our DNA sequence is involved in regulating the less than 2% of the DNA that codes for proteins. In total, Encode scientists say, about 80% of the DNA sequence can be assigned some sort of biochemical function.
Read the rest of the article here: The Guardian