Genetic discrimination is prejudice directed against people who have or may have a genetic disease. Genetic discrimination can involve being denied employment or health insurance. In a healthcare context, it can refer to people being treated based on their genetic status rather than by some more relevant criterion.
Genetic discrimination is the circumstance where somebody's DNA is being used against them in various settings--healthcare, the workplace, insurance, access to disability benefits, even education. Does the university want to look at your DNA before they decide to admit you? That would not be a good thing. This is basically a matter of civil rights; you don't get to pick your DNA. It shouldn't be used against you any more than the color of your skin. And the principle there seems widely adopted. Implementing that got a big step forward in the United States with the passage of the Genetic Information Nondiscrimination Act, because that takes care of this in health insurance and in the workplace. But there are other discriminatory opportunities that we need to continue to be vigilant to prevent.