Purebreed Xenomorphs don't take any of their hosts characteristics, simply using them as a place to incubate until they emerge, however this has only been seen in the game called Aliens versus Predator: Extinction, in other media such as Alien vs. Predator: Requiem, a Predalien (caste) is shown to be a young queen/Praetorian which contradicts Aliens versus Predator: Extinction twice. The first being that according to the game, A Queen (caste) or Praetorian is a purebreed xenomorph and cannot take traits, secondly, the game also has it that a predalien queen is impossible and that only with genetic tampering by Weyland-Yutani was it possible. It seems that only eggs and facehuggers are the only true pure xenomorphs as anything after that requires a host which will cause the embryo to have host traits.
The term Transbreed and Purebreed was first used in Aliens versus Predator: Extinction, but is only a game mechanic.