[private]
We don't have any human genetics. [As strange as it sounds, considering they, according to history, originated from humans.] Purebloods are few and far between so there aren't really very many of us. [It always sounds like she's bragging if trying to explain it. In fact it's been a long while since she's had to.]
The pureblood are the royalty of the vampire world. I guess you could think of it as a pyramid. [Maybe it's easier to explain it the way she was originally taught.]
At the top there are Level A vampires...and at the very bottom are Level E vampires. Both Level D and E were former humans. Where as the Pureblood are Level A...and the Aristocrats are Level B...and so on down the line. The farther down you go the more watered down their blood [And abilities...] becomes.