Don't worry, that's strictly science fiction, the injecting DNA thing. There are probably people experimenting with that sort of thing on stem cells and embryos, but "gene therapy" is a long way from changing a normal into a morph. Don't worry.
What is possibly practical is genome sequencing. In principle it should be possible to do something like the (now basically debunked) dog breed identification test for mixed-breed dogs. So if you have a bunch of poss hets (and I do, ugh), then you can could potentially tell which are the $30 normals and which are the $500 het crazy gene females with just a saliva swab.