How can you tell if a rat is high white? I always got the impression that just blazes were high white, then there was conversation that they're not, etc. etc. So how exactly can you tell this? Also, what about if you bought them from someone else (so you don't know the lineage)- how can you tell what is high white and what is not?

I'm sure this is probably a silly question, but I'd really like to know (: Thanks guys!