Board Thread:WARNING ALL USERS False Info\Spoilers/@comment-96.238.1.154-20130804085459/@comment-1587802-20130804173524

Like people said above, I think turning into a wolf is an ability passed down in the Hale family, because in Visionary, it said that Talia had the rare ability to transform and that's why people respected her. The reasoning behind why Peter's looked more beast-like than Talia and Laura's can either be because: Peter is a male, while Talia and Laura are females; when a Beta, Peter had blue eyes, while Talia and Laura had yellow eyes (just guessing, we don't know for sure); or because Peter killed Laura to become an Alpha, making him more of a beast, whereas Laura assumed the power, and Talia assumed the power too (just guessing).

The reasoning behind Derek not transforming yet is that he doesn't know how to transform. Peter probably figured out how through the supernatural document he said he had backed up on the internet in Season 2 when they were looking at the Kanima files, and because Derek doesn't trust Deaton or Peter or anyone, there's no way he could learn. The production reason for making this story  for Derek is because the beast-like Alpha form costs a lot of money for the CGI to have Derek transform every time he got into a fight, but maybe, he'll figure out how soon and he'll transform in the 3A climax.