8.2 percent of our DNA is ‘functional’

PUBLIC RELEASE DATE:

24-Jul-2014

Contact: University of Oxford News & Information Office news.office@admin.ox.ac.uk 44-186-528-0530 University of Oxford

Only 8.2% of human DNA is likely to be doing something important is 'functional' say Oxford University researchers.

This figure is very different from one given in 2012, when some scientists involved in the ENCODE (Encyclopedia of DNA Elements) project stated that 80% of our genome has some biochemical function.

That claim has been controversial, with many in the field arguing that the biochemical definition of 'function' was too broad that just because an activity on DNA occurs, it does not necessarily have a consequence; for functionality you need to demonstrate that an activity matters.

To reach their figure, the Oxford University group took advantage of the ability of evolution to discern which activities matter and which do not. They identified how much of our genome has avoided accumulating changes over 100 million years of mammalian evolution a clear indication that this DNA matters, it has some important function that needs to be retained.

'This is in large part a matter of different definitions of what is "functional" DNA,' says joint senior author Professor Chris Pointing of the MRC Functional Genomics Unit at Oxford University. 'We don't think our figure is actually too different from what you would get looking at ENCODE's bank of data using the same definition for functional DNA.

'But this isn't just an academic argument about the nebulous word "function". These definitions matter. When sequencing the genomes of patients, if our DNA was largely functional, we'd need to pay attention to every mutation. In contrast, with only 8% being functional, we have to work out the 8% of the mutations detected that might be important. From a medical point of view, this is essential to interpreting the role of human genetic variation in disease.'

The researchers Chris Rands, Stephen Meader, Chris Ponting and Gerton Lunter report their findings in the journal PLOS Genetics. They were funded by the UK Medical Research Council and the Wellcome Trust.

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8.2 percent of our DNA is 'functional'