full blooded or mix?

Question
i just got a new puppy and she looks just like a German Shepherd but how can i be sure she's not a mix? also, we have no clue how old she is. how can i begin to calculate the age of my new puppy? thanks for your time and advice.

Answer
I guess DNA testing has advanced to where you can determine if a dog is a mixed breed.   Try http://www.biopetvetlab.com/dnahome.htm or http://www.wisdompanel.com/

A very young puppy will have a full set of small, tightly teeth.  By 3-4 months, there will be gaps between the teeth where the jaw has grown and bigger teeth poking through here and there, often starting in the front.  At 5-6 months, most of the baby teeth are gone except the needle like canines.  They will finally go before too much longer.  The Puppy will then have a full set of uniformly large teeth with no gaps.  

A vet visit soon would be a good idea.  Unless you know she has had shots, the vet will need to give her some.  You also want a heartworm test and preventative.  The vet may be able to give a better idea of her age.