From John Timmer at Ars Technica:
Why are people excited about Kelly’s DNA? The simple answer would seem to be that he has an identical twin, who must have identical DNA, and so we have a chance to see what space does to DNA. After all, space is a high-radiation environment, and we know that radiation damages DNA.
But there’s quite a bit more to it than that. First and foremost, the Kelly twins’ DNA is not identical. Every time a cell divides, it typically picks up a mutation or two. Further mutations happen simply because of the stresses of life, which expose us all to some radiation and DNA-damaging chemicals, no matter how careful we are about diet and sunscreen. Over the years, the Kelly twins’ cells have undoubtedly picked up collections of distinctive mutations.
As a result, the more relevant comparison (and one NASA did) is Scott’s DNA before and after his time in space. That can tell us how many changes were picked up while in space. But as noted above, he would have probably picked up some mutations even if he sat here on Earth. And that’s where his twin Mark, who did sit here on Earth, comes in. Mark’s before and after gives us a sense of the normal background rate of mutation on Earth. Comparing that rate to Scott’s tells us the important number: the degree to which this rate is elevated in the environment of low-Earth orbit.
But mutations alone don’t tell the full story. Less than three percent of a person’s DNA is translated into the proteins that perform the functions in our cell. So chances are good that any mutations Scott picked up would have missed his genes entirely.
But the DNA sequence of a gene isn’t the only way to influence its behavior. Our environments influence gene activity all the time—our bodies change gene activity to respond to everything from hostile pathogens to the time of day.More.
By all means, read the whole thing. But note: The Central Dogma of evolution is dead (one gene, one protein…). But many tenures lie between that fact and letting the public know that our genes are a largely uncharted sea.
See also: Now THAT’S different: Identical twins, one in space, have different DNA? Obviously, the genome is much more plastic than centuries of hereditarians have led us to believe. It will eventually be very difficult to explain Darwinism to students. Somewhat like explaining phrenology maybe…
About that Central Dogma (Cornelius Hunter)