I think the only way to get a predalien queen is through humans messing around. Look at all the queens in the movies and compare them to aliens born from humans. The two don't look too much alike. Most likely the queens we've seen came from humans. Now look at Chet, the only thing that really gives it way as a young queen in the movie is it's head. Aside from that, predalien look a lot like human born aliens(besides the mandibles and dreds). I'm guessing that as a young queen matures it looks less like a standard alien and more like a queen. I think that if Chet had time to fully grow it would have looked like a normal queen. That way, a queen would still be a purebred but praetorians might be transbred until they change. With a pure queen, the eggs would be pure. If she wasn't, you would get Alien Ressurection.
