[A]rticles claiming that the mission activated Kelly's “space genes,” that 7 percent of his genes didn't return to normal post-spaceflight, and that he and Mark are no longer identical twins..... these stories are biologically impossible. If 7 percent of Kelly's genome was altered, he would be about as different from a human as a rhesus monkey. ... Your genome dwells inside the nuclei of your cells. Think of it as an instruction manual: It is the complete set of DNA that describes the form and function of every aspect of your being, with each gene pertaining to a particular task life requires. But this manual...