My understanding is that the answer is yes. To be θ(n) implies O(n), which itself implies O(n^2).
In other words, a function that is tightly bounded by n is trivially upper-bounded by n^2 as well.
The TA of my class tells me that I'm wrong, that a function that is tightly bounded by n cannot be upper-bounded by anything other than n. Which doesn't sound right to me, as O(n) is but a subset of O(n^2).