Astronaut Scott Kelly’s DNA no longer matches that of his identical twin after time in space, revealed NASA Twins Study.

The findings showed that after returning to Earth, Scott started the process of readapting to Earth's gravity. Most of the biological changes he experienced in space quickly returned to nearly his pre-flight status.
While 93 per cent of Scott's genes returned to normal after landing, seven per cent remained unchanged.
This remaining seven per cent points to the possible longer term changes in genes related to his immune system, DNA repair, bone formation networks, hypoxia and hypercapnia, the US space agency said in a statement.
By measuring large numbers of metabolites, cytokines and proteins in Scott's body the team learnt that spaceflight is associated with oxygen deprivation stress, increased inflammation and dramatic nutrient shifts that affect gene expression.
Previous studies showed the effect on the body after the standard-duration six-month missions aboard the International Space Station (ISS).
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The results were presented at the annual Human Research Program Investigators' Workshop held in Texas.
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The one-year resulted in no significant decreases in Scott's cognitive performance.
However, a more pronounced decrease in speed and accuracy was reported postflight, possibly due to re-exposure and adjustment to Earth's gravity, and the busy schedule that enveloped Scott after his mission, the agency said.
Source-IANS