They’re 99.999% the same — until one ends up in space, the other doesn’t
Genetic-sequencing tools that plumb our biology in more detail than ever are providing new answers to why we get sick or act and look the way we do. In this era of molecular genetics, scientists can pinpoint which genes are linked to diseases — and more recently, whether certain genes are turned on and off over time — a field known as epigenetics.
“We can tease out more of the genetic components of nature-versus-nurture,” says Christopher Mason, a geneticist at Weill Cornell Medicine in New York. When identical twins are born, they’re 99.999 per cent the same, but as they age, the effects of lifestyle, trauma, stress or disease cause their genes to be expressed in distinct ways. “They experience the slings and arrows of the environment differently,” he says. “Twin studies help you see the drivers of change.”
In one of the purest twins experiments ever designed, Mason was part of the team that compared the effects of a year spent in space on 52-year-old American astronaut Scott Kelly with the Earth-based experience of his identical twin, Mark. Researchers discovered that Scott Kelly’s time on the International Space Station had altered the expression of 7 per cent of his genes, including those involved in blood oxygenation and DNA repair.
Mason says the research offers insight into how to study the effects of harsh environments. “We want to leverage the capacity of twin studies to understand human physiology at extremes, such as scuba diving, climbing Mount Everest or flying fighter jets,” he says.