Question about domain mapping

Greetings,

I've read through several messages about domain mapping and my poor head is swirling a little bit with contradictory information so I'm hoping someone wise can set me straight:

We have an install at, say, whatitis.com with multiple blogs.

Each blog will have its own subdomain AND domain, i.e. who.whatitis.com will also have whowhatitis.com on it.

My question is -- is it possible to have it so the full domain, whowhatitis.com be fully used throughout the who.whatitis.com site rather than simply be redirector or parked domain?

If I'm not clear enough on this, let's say user goes to who.whatitis.com/about.php -- will it also work if they go to whowhatitis.com/about.php and if they click around, it will stay whowhatitis.com?

Thanks!
Ray