On Sunday, March 11 we published an article on how space changed about seven percent of Scott Kelly’s Genes. It turns out that is not true at all.

CNN, USA Today, Time, HuffPost, LiveScience, and others, also wrote about this. According to Prof. Chris Mason, a professor at Weill Cornell Medicine, this is not true.

Prof. Mason led the NASA-backed “Twins Study”. The study closely monitored Kelly’s body and genes during his two-year stint in space, thus, comparing them against those of his identical twin brother.

When Scott Kelly went into space, his DNA remained fundamentally the same. What changed was the way his DNA was transcribed and translated into functional products; the study of such shifts is called epigenetics. These epigenetic changes were likely the body’s way of responding to the low gravity, oxygen deprivation, increased inflammation and diet challenges of spaceflight.

Professor Mason reported epigenetic changes in five biological pathways, including those related to oxygen deprivation, DNA repair and bone formation.

Our DNA is about two percent different from that of a chimp. If seven percent of Scott’s DNA changed, he would have basically been a different species.

In a press release from NASA, researchers reported hundreds of unique mutations in the DNA of both Scott and Mark Kelly (his identical twin brother). That is something scientists had expected but is nowhere near the “no longer identical twins.”

Their DNA does differ — but so does the DNA of all humans, even twins, thanks to mutations that accumulate normally over the course of a lifetime.

While his genes remained the same, what changed was his gene expression — the activity of his cells, using that same genetic code, in deciding when and what proteins to manufacture.

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Thumbnail image: Scott Kelly during his period inside the International Space Station.