91.8% of human DNA may be junk
DNA mostly 'junk?' Only 8.2 percent of human DNA is 'functional', study finds
July 24, 2014
University of Oxford
Only 8.2 percent of human DNA is likely to be doing something important -- is 'functional' -- say 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.
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.'
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