The key participants in the experiment were brothers Scott and Mark Kelly. The first of them spend almost a year on the ISS. Upon Scott’s return, he and Mark were carefully examined, and it was found that Scott had developed a number of genetic mutations in orbit, some of which persist to this day. Scientists do not make any judgements about them yet.
When Scott returned to Earth, end sections of his chromosomes were doubled in length. But on the third day, the astronaut’s telomeres came back to their normal values.
Scientists explained that about 7% of Scott’s genetic mutations still remained. First of all, they concern the production of proteins. The stress experienced by an astronaut while being in space affects his body causing it to «make mistakes».
NASA assures that the deviations are minimal, but their future effects are difficult to predict. Therefore, Scott will continue to be monitored, and the information obtained will benefit the entire mankind.