explain better ....
when you pair a large dog with a small dog, the puppies are identical to the mother, and this is something unreal, should also resemble the father and have mixed characteristics. (color and type of hair and personality).

Sorry for my English   

Thanks goes well this answer     

would be nice to have friends with dogs to live free without that horrible fence

You can do that?

There is something to make sure that dogs ofdifferent sizes and cross have puppy not only clones of the mother?

This is very unpleasant!!