75% of the Human Genome Is Junk DNA, Claims New Research

New research by Professor Dan Graur shows that only a quarter of the human genome is functional. 

How much of the human genome, our genetic blueprint, actually makes us who we are? New work by an evolutionary biologist at the University of Houston suggests that only up to 25% of the human genome is functional. The other 75% are so-called “junk DNA” - useless sequences that don’t play a role in the important chemical reactions inside us. This conclusion goes sharply against the estimate of 80% functionality proposed by the ENCODE project, an international public research consortium that has led the way in human genome exploration.

Dan Graur, professor of biology and biochemistry, calculated that about 10 to 15 percent of the genome is actually functional, with the upper limit of 25 percent. 

His reasoning stems from looking at how mutations affect a population’s DNA. Graur’s mathematical model allowed him to calculate the “mutational load” - the total genetic load of a population that results from the accumulation of bad or deleterious mutations. At some point the load can become too much and the population would go extinct.  

Graur’s work related how reproductive success, the ability of a species to replenish itself, was decreased by the deleterious mutations. Over time, humans would have to reproduce at an impossible high rate to keep up with the mutations, Graur concluded.

The professor explained why he finds the 80% functionality of the genome proposed by the ENCODE scientists as unrealistic:

“For 80 percent of the human genome to be functional, each couple in the world would have to beget on average 15 children and all but two would have to die or fail to reproduce,” writes Graur. “If we use the upper bound for the deleterious mutation rate (2 × 10−8 mutations per nucleotide per generation), then … the number of children that each couple would have to have to maintain a constant population size would exceed the number of stars in the visible universe by ten orders of magnitude.”

This is not the first time Graur fought against the 80% claim. In a 2014 interview with Science magazine, Graur even claimed its proponents are essentially pitching the idea of “intelligent design”. To Graur, asserting 80% usability implies that most of the genome exists to serve a purpose. Instead, he believes that “everything is shaped by evolution,” a slow process that weeds out useless features through genetic mutations - the drivers of evolution. This process also accumulates a lot of junk in the human genome.

Why is it important to know that only a quarter of the human genome may have functionality? Graur believes his work can shift the focus in the field of human genomics to what is useful from a medical standpoint: 

“We need to know the functional fraction of the human genome in order to focus biomedical research on the parts that can be used to prevent and cure disease,” said Graur. “There is no need to sequence everything under the sun. We need only to sequence the sections we know are functional.” 

You can read the study here in Genome Biology and Evolution. 

LinkedIn meets Tinder in this mindful networking app

Swipe right to make the connections that could change your career.

Getty Images
Swipe right. Match. Meet over coffee or set up a call.

No, we aren't talking about Tinder. Introducing Shapr, a free app that helps people with synergistic professional goals and skill sets easily meet and collaborate.

Keep reading Show less

Think you’re bad at math? You may suffer from ‘math trauma’

Even some teachers suffer from anxiety about math.

Image credit: Getty Images
Mind & Brain

I teach people how to teach math, and I've been working in this field for 30 years. Across those decades, I've met many people who suffer from varying degrees of math trauma – a form of debilitating mental shutdown when it comes to doing mathematics.

Keep reading Show less

A world map of Virgin Mary apparitions

She met mere mortals with and without the Vatican's approval.

Strange Maps
  • For centuries, the Virgin Mary has appeared to the faithful, requesting devotion and promising comfort.
  • These maps show the geography of Marian apparitions – the handful approved by the Vatican, and many others.
  • Historically, Europe is where most apparitions have been reported, but the U.S. is pretty fertile ground too.
Keep reading Show less

How KGB founder Iron Felix justified terror and mass executions

The legacy of Felix Dzerzhinsky, who led Soviet secret police in the "Red Terror," still confounds Russia.

Getty Images
Politics & Current Affairs
  • Felix Dzerzhinsky led the Cheka, Soviet Union's first secret police.
  • The Cheka was infamous for executing thousands during the Red Terror of 1918.
  • The Cheka later became the KGB, the spy organization where Russia's President Putin served for years.
Keep reading Show less