The rest of our genome is nothing but leftover evolutionary material – parts of the genome that have undergone losses or gains in the DNA code - often called "junk" DNA.

To reach their figure, the Oxford team identified how much of our genome has avoided accumulating changes over 100 million years of mammalian evolution - a clear indication that this DNA matters and it has some important function that needs to be retained.

"This is... a matter of different definitions of what is 'functional' DNA," says Chris Pointing, professor of MRC Functional Genomics Unit at Oxford University.

"We do not 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," he said.

In 2012, some scientists involved in the Encyclopedia of DNA Elements (ENCODE) project stated that 80 percent of our genome has some biochemical function.

"In contrast, with only eight percent DNA being functional, we have to work out the eight percent of the mutations detected that might be important. This is essential to interpreting the role of human genetic variation in disease," Pointing said.

A little over one percent of human DNA accounts for the proteins that carry out almost all of the critical biological processes in the body.

The other seven percent is thought to be involved in the switching on and off of genes that encode proteins - at different times in response to various factors and in different parts of the body.

Interestingly, only 2.2 percent of human DNA is common with mice.

"The fact that we only have 2.2 percent of DNA in common with mice does not show that we are so different. We are not so special. Our fundamental biology is very similar," said Gerton Lunter from the Wellcome Trust Centre for Human Genetics at Oxford University.

The findings were shared in a paper appeared in the journal PLOS Genetics.


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