Despite the complex structure of the human genome, more than 90 percent from it doesn’t have important biological function, scientists from Oxford University report in research published in the July 24 edition from the journal PLOS Genetics.
In fact, according to the study authors, just 8.2 percent from the genome is actively operating to make us who we’re and our cellular systems functioning. The rest, Telegraph science correspondent Sarah Knapton wrote on Friday, is a mixture of leftover material from our evolutionary past, or doesn’t have function whatsoever.
The new percentage is really a far cry from previous claims, produced by ENCODE (Encyclopedia of DNA Elements) project scientists in 2012, that 80 percent of the human genome possessed some form of biochemical function. The Oxford researchers noted those controversial claims left most professionals disputing the ENCODE’s team’s broad meaning of function, which ought to be demonstrated that activity occurring on DNA has a reason for happening.
In reaching the 8.2 percent figure, the authors from the PLOS Genetics study said they worked to recognize how much of the genome has avoided changing or evolving in the last 100 million years, as this serves to indicate these pieces of genetic code possess some important function which must be preserved and maintained.
“This is within large part dependent on different definitions of what is ‘functional’ DNA,” joint senior author Professor Chris Pointing of Oxford’s MRC Functional Genomics Unit said in a statement. “We don’t think our figure is actually too different from what you will get looking at ENCODE’s bank of information utilizing the same definition for functional DNA.”
“But this isn’t just an academic argument about the nebulous word ‘function’. These definitions matter,” he added. “When sequencing the genomes of patients, if our DNA was largely functional, we’d need to pay attention to every mutation. In contrast, with simply 8 percent being functional, we must work out the 8 percent from the mutations detected that might be important. From a medical perspective, this really is necessary to interpreting the role of human genetic variation in disease.”
Of the running 8.2 percent, a little more than one percent of human DNA makes up about the proteins required to execute nearly all of your body’s essential biological processes, Knapton said. Another seven percent is believed to play a job in activating or deactivating genes that encode proteins in response to various factors, at different times and in different parts of your body. They are referred to as control and regulation elements.
Researchers Chris Rands, Stephen Meader, Chris Ponting and Gerton Lunter used a computational approach to compare the complete DNA sequences of humans with those of other mammals, including mice, rabbits, dogs and horses. Their plan was to find where chunks of DNA were inserted into or deleted from the mammals’ genome, which occurred randomly except when natural selection acted in order to preserve DNA considered to be functional.
“We discovered that 8.2 percent in our human genome is functional,” concluded Dr. Gerton Lunter from the Wellcome Trust Centre for Human Genetics at Oxford. “We cannot tell where every bit of the 8.2 percent of functional DNA is within our genomes, but our approach is largely free from assumptions or hypotheses. For example, it’s not depending on what we know concerning the genome or what particular experiments are used to identify biological function.”
