Astronaut Scott Kelly's DNA was altered during his year in space, and seven percent of his genetic code remains changed, according to research conducted by NASA.
Kelly spent one year aboard the International Space Station, and returned to Earth two years ago. Ten research teams looked at what happened to him through an extensive comparison with his identical twin, Mark, who stayed on Earth, and presented their findings at the annual NASA Human Research Program Investigators' Workshop in Texas in late January.
The Kelly twins are the only identical twin astronauts in history.
Scott Kelly came back a little taller, his gut bacteria were completely different and his body mass had decreased. But his genetic code had dramatically changed. Ninety-three percent of Scott's genetic expression returned to normal, but "the remaining 7 percent point to possible longer term changes in genes related to his immune system, DNA repair, bone formation networks, hypoxia, and hypercapnia."
The changes are "thought to be from the stresses of space travel, which can cause changes in a cell's biological pathways," the NASA statement said. "Such actions can trigger the assembly of new molecules, like a fat or protein, cellular degradation, and can turn genes on and off, which change cellular function."
Chris Mason of Weill Cornell Medicine focused on chemical changes in RNA and DNA, and whole-genome sequencing revealed each twin has "hundreds of unique mutations in their genome, more than expected, and some were found only after spaceflight."
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