Down Syndrome is a spectrum disorder, and different people are affected differently by it. For example, there are people such as Chris Burke
who are able to speak, write, hold jobs, etc. There are also people like the guy with Down Syndrome who is so severely retarded that he mostly just stands around and drools (NOTE: I am NOT making fun; just stating a fact.).
Has there ever been a case where an individual had the 21st chromosome, who perhaps even had the physical characterstics of Down Syndrome, but who had an average or even above-average IQ?