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
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.