MMR in normal games, up until season 11, did not affect your ranked MMR and didn't play a part in ranked matchmaking. ... Ranked Seeding is a process through which the game determines your skill level by analyzing your normal games before matching you with other players in ranked.

Do norms affect your MMR?

If you keep playing normals, you'll end up playing against better and better players, as your MMR rises. The only place where your MMR from other queues is taken into account is when you're playing team ranked 5/3.

Is normal and ranked MMR separate?

They are separate. You can have high normals MMR with low ranked MMR, and vice versa. It's rare for them to be the same.