Talking about biology as though it assigns gender is problematic, though. It implies that genitals=gender, which is obviously not the case. Saying that cisgender folks' gender "matches" their sexual phenotype is really just used as a justification for cissexism (because transgender folks' gender "doesn't match"), and it's false to boot: biological sex is gender-neutral. We still have only gendered terms to talk about sexual characteristics, which is unfortunate and perpetuates the idea of "matching."
Sex doesn't imply gender
<3
-Jesse