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.
Is race a trivial quality of humans, or of deep social importance? Who gets to decide whether race exists or not?
How many different races are there? Pick a number, any number, says philosophy professor Philip Kitcher. Wherever there is an agenda there is a division to be made; race is a social construct with scientific levers. "If there’s one thing that we’ve learned from biological science and psychological science over the last century, it’s that there’s an enormous amount of variation within the groups that we’ve traditionally thought of as races, far more than there is between the groups we’ve traditionally thought of as races." This makes sense; historically, we've drawn the line wherever it has suited the mainstream agenda. Humanity can be divided into two races, which would see Africans, Europeans and most Asians as one unified race. Or it could be divided into three races, which would separate Africans into their own group. You can keep dividing humanity down into more and more refined biological groups until you have 10 or 20 or 30 different races. But what would be the purpose? Our mistake has always been confusing groups for classes anyhow. Philip Kitcher is the co-author of The Seasons Alter:How to Save Our Planet in Six Acts.
Harvard bioethics specialist Glenn Cohen considers the complex question of whether humans should mix their genetic material with other animals to create chimeras.
It is really, really fun when Harvard professors play ‘What If…’. This is a regular part of Glenn Cohen’s work as a law professor specializing in health policy, bioethics and biotech. Invoking the Jurassic Park rule of ‘just because you can, doesn’t mean you should’ and imagining all eventualities is how Cohen explores the fascinating and sometimes twisted intricacies driving our ethical dilemmas.
It’s particularly fun on the topic of chimeras, which broadly defined is research that mixes human and animal genetic material. Cohen lists some real cases as examples: mixing human brain cells into mice brains, or humanizing a mouse’s immune system to carry out studies that yield results relevant to humans. Former U.S. senator Jesse Helms had a pig valve placement in his heart many years ago. To make a more imaginative leap, what about a gorilla with a human face? How would we feel about that?
Cohen discusses a few key ethical arguments surrounding our hesitancy to mix interspecies genetic material, then moves onto a hypothetical concerning Sesame Street’s Big Bird, and surmises that when it comes to this ethical area, decisions can really only be made on a case by case basis. Some changes simply are more unethical or sociologically disturbing to humans, and here Cohen cites his friend and colleague at Stanford Law School, Professor Henry T. Greely, who sums it up nicely with three words: brains, balls, and faces. Those are the things that make us most uncomfortable in genetic mixing, perhaps because they are definitive markers of what it is to be human.
The jury might be out on chimeras, but at least you have some insight into how a bioethicist’s mind works.
Glenn Cohen's book is Patients with Passports: Medical Tourism, Law, and Ethics.