NB Title of this post (and the movie) stealth corrected *blush* props to Gil
This movie is set in a dystopia where genetic determinism rules. Go watch it immediately.
Having a genetic defect is something that it might be rational to choose not to know about. Such knowledge can be paralysing, and can also become a self-fulfilling prophecy.
It is also possible greatly to exceed the expectations of others, which can put limits on what one is permitted to attempt. The knowledge being genetic helped make the point very starkly, because of its supposed objectivity despite the major role of probability in forecasting; the film also reminded me how limiting expectations and assumptions about the interests, strengths and weaknesses of our family members can be.
Sometimes it is morally right to pretend to be something you are not, if society is morally wrong about something. I am reminded of the hoo-haa in the Church of England Cathedral world some years ago when a candidate for an alto singing job put only their initial and surname on their very impressive application. It was only when the candidate turned up for interview that the panel discovered that she was a woman, and therefore ineligible, whether or not her voice would have blended superbly.