Man's DNA no longer matches his twin's after a year in space

Man's DNA no longer matches his twin's after a year in space

"Mark and Scott Kelly are still identical twins; Scott's DNA did not fundamentally change", NASA said. "It turns out that big changes in the expression of Scott Kelly's genes occurred while he was in space, and 7 percent of those changes persisted after he returned to Earth, lead author Susan Bailey, a researcher at Colorado State University, who led the research on Kelly, told Nat Geo's Nadia Drake", Live Science's correction explained. NASA made it clear in a secondary statement that "the change related to only 7 percent of the gene expression that changed during spaceflight that had not returned to preflight after six months on Earth". A twin study has now discovered that spending 1 year in space causes considerable changes in an astronaut's genes, altering DNA by almost 7 percent.

To track physical changes caused by time in space, scientists measured Kelly's metabolites (necessary for maintaining life), cytokines (secreted by immune system cells) and proteins (workhorses within each cell) before, during and after his mission. That's more than would be expected, but nowhere near enough to make the duo "no longer identical twins".

NASA astronaut Scott Kelly, left, and his twin Mark. "What researchers did observe are changes in gene expression, which is how your body reacts to your environment".

The long-term effects of space habitation are still unknown and the space agency said the experiment was a stepping stone for its mission to Mars. For the so-called "year in space", Kelly spent 340 consecutive days on the ISS, ending in March of 2016.

Although 93% of Kelly's genetic expression returned to normal once he returned to Earth, a subset of several hundred "space genes" remained disrupted. However, the remaining 7% point to possible longer term changes in genes related to his immune system, DNA fix, bone formation networks, hypoxia, and hypercapnia.

Mark (left) and Scott (right) Kelly. NASA

It is known that astronauts' bodies adapt to micro-gravity, but it was generally assumed the effects wore off upon their return to Earth. Indeed, if seven percent of his DNA changed, he would literally be a different species.

They have also verified that Kelly's telomeres - the caps on the ends of chromosomes - grew to be longer than Mark's.

NASA says research like this is needed before astronauts are sent on journeys like a planned three-year mission to Mars.

But you wouldn't know that from reading some of the coverage the January announcement inexplicably spawned this week - articles claiming that the mission activated Kelly's "space genes", that seven per cent of his genes didn't return to normal post-spaceflight, and that he and Mark are no longer identical twins.

Researchers are now evaluating what impact the findings might have upon space travel beyond Earth's orbit.

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