If the dog is of good nerve with balance in the drives and temperament the aggression will only come out when necessary. That does come from genetics, not so much the training or socializing the dog has had.
If your puppy is fearful and shows reactive aggression that is fear based, it is genetic.
Ahhh... Not good, like he growled at my grandmother when she came in my room and I've never had a puppy growl nonplayfully.. So yeah, it kinda threw me off a bit