Excerpt From Geek.com (full article linked below)
After spending nearly a year aboard the International Space Station, American astronaut Scott Kelly returned to Earth in 2016—only to find that his DNA had changed.
“Scott’s telomeres (endcaps of chromosomes that shorten as one ages) actually became significantly longer in space,” according to NASA. Unfortunately, the growth spurt didn’t last long; the majority of those telomeres shrunk within two days of landing.
“Another interesting find concerned what some call the ‘space gene,'” the Administration said.
Researchers believe that 93 percent of Scott’s genes have returned to normal. The remaining 7 percent, however, suggest long-term changes in genes related to the immune system, DNA repair, bone formation networks, hypoxia, and hypercapnia.
https://www.geek.com/science/astronaut-scott-kellys-dna-changed-in-space-1733389/