Some people worry whether genetically engineered plants and animals are safe. Other people worry that genetic engineering will eventually crossover to humans and become a privilege of the wealthy "who will opt to design their child with genetic advantages." There are arguments both for and against human genetic engineering, including "the belief that every fetus has an inherent right to remain genetically unmodified, the belief that parents hold the rights to modify their unborn offspring, and the belief that every child has the right to be born free from preventable diseases."*
The GloFish (patented and trademarked) is a brand of genetically modified fish.
And if you really want to be freaked out by this subject, look up spider-goats.