An opening phrase to introduce an quickly stated question or statement. Typically a ghetto one that many can relate to. The 'du' can be substituted by other words such as; can, will, were and etc. The 'ya' can also be subtituted for he/she/it/they and other verbs.
Example one
Rhonda: Hey Bern, can i borrow your lipliner
Bern: Sure, Butdu ya gotta be breathen and swipin so hard when ya do.
Example two
Mtn Climber one: Hey, it that the mayor? I heard he comes here often.
Mtn Climber two: Butcan he pass a bill?