I'm just curious cause if he came out of that vad of chemicals chalk-white and with green hair and a big grin, does that make him genetically altered? Or what if he was already a mutant before?

.........................NOOOOOOOOOOOOOOO. .....I'm sorry......I don't quite know where that came from

Well he could be?

I doubt it actually altered his DNA, but it did change his body in more ways than just making him look like a clown. In Salvation Run, he states the chemicals still burn his skin.

I keep hearing something about him having acidic blood too. And he's more than just crazy too... his "super-sanity" or whatever is a borderline superhuman ability. I think I'd count him as genetically altered.

No, his appearance and mentality were simply altered.

Joker isn't a mutant, but because of his abnormal history of facing death countless time has recognized him possibly being something more than being human.

The one from the batman animated series appeared so

He's possibly mutated, but when most people think of the term 'mutant', they think of people like the X-Men, who were born with said mutation. Joker was not. He was not born with any genetic aberration of any kind. When he fell into that vat of chemicals, was he genetically altered? Possibly. He was certainly cosmetically altered, but it's been shown that his hair turning green, his skin turning white happened to anyone those chemicals fell onto. I imagine his insanity comes from ingesting it, the effects of which were not shown on another subject.

@JonSmith said:

He's possibly mutated, but when most people think of the term 'mutant', they think of people like the X-Men, who were born with said mutation. Joker was not. He was not born with any genetic aberration of any kind. When he fell into that vat of chemicals, was he genetically altered? Possibly. He was certainly cosmetically altered, but it's been shown that his hair turning green, his skin turning white happened to anyone those chemicals fell onto. I imagine his insanity comes from ingesting it, the effects of which were not shown on another subject.

I believe original poster is referring to Teenage Mutant Ninja Turtles terminology of "mutant", with the critters, humans, even some plant species, exposed to mutagen = mutant.