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Global study counters 'junk' DNA theory

10 September 2012
Appeared in BioNews 672

Scientists have found that 80 percent of DNA in the human genome, previously thought to be of no use, have important functions. This discovery dismantles the 'junk' DNA theory after years of uncertainty.

The revelation was published last week as part of the most comprehensive analysis of the human genome to date. The project, known as the Encyclopedia of DNA Elements (Encode) involved over 400 scientists at 32 institutions worldwide.

The nickname 'junk' DNA was coined many years ago to describe the DNA present in many genomes that doesn't code for proteins, and therefore did not appear to serve any clear function. The completion of the Human Genome Project a decade ago revealed that only 2 percent of human DNA coded for proteins, while the rest appeared to have no purpose. Encode was launched in 2003 to further investigate the genome.

Now, after almost ten years, researchers have arrived at the conclusion that the majority of non-coding DNA actually plays a pivotal role in keeping the body running. These stretches of DNA act as regulatory switches that control whether certain genes are switched on or off in specific cells.

'We always knew that protein-coding genes were not the whole story', Dr Ewan Birney from the European Bioinformatics Institute, who led the project, told Wired. 'A much bigger part of the genome - a surprising amount, in fact - is involved in controlling when and where proteins are produced, than in simply manufacturing the building blocks'.

The team found over four million switches among the 98 percent of non-coding DNA formerly thought to be 'junk'. Many of these are located in completely different areas of the genome to the genes they control, which is perhaps why, until now, they remained undetected.

The findings could open up a new chapter in medical research, according to Professor Mike Stratton, director of the Wellcome Trust Sanger Institute. 'The Encode project will change the way many researchers conduct their science and give those who seek to understand disease a much better grasp of where genetic variation can affect our genome for ill'.

Dr Birney adds: 'Many of the switches we have identified are linked to changes in risk for conditions from heart disease to diabetes or mental illness. This will give researchers a whole new world to explore and ultimately, it's hoped, will lead to new treatments'.

It may, however, be some time before patients start to benefit from these new insights, as scientists must first detangle the complex pathways that exist within the newly discovered genetic control panel.

Detailed map of genome function
BBC News |  5 September 2012
Encode study debunks 'junk DNA' theory
Wired |  6 September 2012
Scientists debunk 'junk DNA' theory to reveal vast majority of human genes perform a vital function
Independent |  5 September 2012
There’s no junk DNA – it all has a purpose, say scientists
Scotsman |  6 September 2012
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