None of these things are true. You don’t put chemicals into something in order to genetically modify it. Genetic modification happens in laboratories when genes from one organism are inserted into another. We all eat genetically modified crops daily (at least if you live in the US.)
And yes, you might eat some GM wheat if you go to McDonald’s. But also you will likely eat GM wheat if you buy bread at the store or go to any restaurant that serves sandwiches.
McDonald’s beef contains three ingredients, beef, salt, and pepper. I mean, I can’t really believe I’m defending McDonald’s right now. I don’t think they’re, like, /good/. I just don’t understand why people think it’s worse for you than a comparable hamburger from anywhere else.