Keith's note: Yes, Twitter has its limitations when it comes to saying things in 140 characters. But if CASIS is tweeting pseudoscience like this (or misquoting someone) on behalf of NASA then they need to be shut down. On Earth, a "genome" is made out of DNA (or RNA) - period. How can you "change a genome" unless you do something to the nucleic acid (DNA or RNA) that comprises the genome? And if you are going to "change a genome", well that kind of falls right in the realm of what a GMO (Genetically Modified Organism) is.
Keith's update: CASIS just tweeted this reply. Alas, there is still some basic Biology ignorance in evidence on the Tweeter's part. When you start to deliberately modify gene expression in an organism you 1. are tinkering with DNA since form (structure) = function and 2. you have one foot clearly in the GMO concept - and the other about to step in.
Keith's 22 Oct update: Zero Gravity Solutions sent NASA Watch an email today regarding the @NASAWatch response to what @ISS_CASIS tweeted yesterday: "We would request the clarification to state: We are changing the genome expression without adding foreign genes."