Subscribe to the BioNews newsletter for free

Login
Advanced Search

Search for
BioNews

Like the Progress Educational Trust on Facebook


The Fertility Show


 

Only eight percent of DNA is 'functional'

04 August 2014

By Chris Baldacci

Appeared in BioNews 765

Researchers at the University of Oxford have estimated that only 8.2 percent of human DNA has been left unchanged as the species has evolved and is therefore likely to be functional.

The team worked with the hypothesis that over millions of years of evolution, natural selection would keep the most useful sections of DNA relatively unchanged across a whole host of related species because they were the genes that were advantageous.

Looking for insertions and deletions in DNA sequences, the team analysed the genomes of a number of mammals including mice and humans to see which sections of DNA contained changes few and far between and had been 'preserved'. It was these areas of the genome that the Oxford University team classified as likely possessing some important function.

'Throughout the evolution of these species from their common ancestors, mutations arise in the DNA and natural selection counteracts these changes to keep useful DNA sequences intact', Dr Gerton Lunter from the Wellcome Trust Centre for Human Genetics at Oxford University and joint senior author of the paper said.

'We found that 8.2 percent of our human genome is functional', said Dr Lunter. 'We cannot tell where every bit of the 8.2 percent of functional DNA is in our genomes, but our approach is largely free from assumptions or hypotheses. For example, it is not dependent on what we know about the genome or what particular experiments are used to identify biological function'.

The figure differs significantly from that given by some of the researchers involved in ENCODE, who stated that 80 percent of the genome has some biochemical function, leading to a debate over the definition of the word 'functional' (reported in BioNews 672).

'This is in large part a matter of different definitions of what is "functional" DNA', explained joint lead author Professor Chris Ponting of the MRC Functional Genomics Unit. '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', he continued.

'In contrast, with only eight percent being functional, we have to work out the eight percent 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 remainder of the human genome is made up of leftover evolutionary material and is known as 'junk' DNA. Dr Lunter said ‘We haven't been designed. We've evolved and that's a messy process. This other DNA really is just filler. It's not garbage. It might come in useful one day. But it's not a burden'.

Comparing the genomes across different species, the researchers also observed that humans share 2.2 percent of their function DNA with mice. Professor Pointing said: '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'.

'Biologically, humans are pretty ordinary in the scheme of things, I'm afraid'.

RELATED ARTICLES FROM THE BIONEWS ARCHIVE

24 July 2017 - by Ipsita Herlekar 
Almost 75 percent of the human genome is 'junk DNA', suggests a new study...
17 August 2015 - by Isobel Steer 
Compared to ancestral humans, most modern people have lost 40.7 million base pairs of DNA...

28 October 2013 - by Dr Naqash Raja 
Regions of the genome that do not code for proteins have been found to shape facial features, research at the Lawrence Berkeley National Laboratory, USA, has shown...
10 September 2012 - by Emma Stoye 
Scientists have found that 80 percent of DNA in the human genome, previously thought to be of no use, have important functions...
29 March 2010 - by Dr Will Fletcher 
A recent study has lent more weight to the view that 'Junk DNA' may be anything but junk. A joint effort by the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany and Stanford University, California, US, has uncovered large differences between the non-coding DNA of different individuals, which may be associated with differing levels of disease risk and other traits too...
19 June 2007 - by Stuart Scott 
The universally accepted maxim that genes are transcribed into RNA and subsequently translated into proteins, a concept that has underwritten huge swathes of research in the last 40 years, has been significantly muddied. A groundbreaking Nature paper has shown the road from genome to protein is much...

HAVE YOUR SAY
Be the first to have your say.

You need to or  to add comments.

By posting a comment you agree to abide by the BioNews terms and conditions


- click here to enquire about using this story.

Published by the Progress Educational Trust

CROSSING FRONTIERS

Moving the Boundaries of Human Reproduction

Public Conference
London
8 December 2017

Speakers include

Professor Azim Surani

Professor Magdalena Zernicka-Goetz

Professor Robin Lovell-Badge

Sally Cheshire

Professor Guido Pennings

Katherine Littler

Professor Allan Pacey

Dr Sue Avery

Professor Richard Anderson

Dr Elizabeth Garner

Dr Jacques Cohen

Dr Anna Smajdor

Dr Andy Greenfield

Vivienne Parry

Dr Helen O'Neill

Dr César Palacios-González

Philippa Taylor

Fiona Fox

Sarah Norcross


BOOK HERE

Good Fundraising Code

Become a Friend of PET HERE and give the Progress Educational Trust a regular donation