"Nature vs nurture" is an old debate that has not yet been concluded and data is hard to obtain. But it seems at the moment that how you training and upbringing has more impact on how an animal develops.
Also, i was more speaking ofphysical traits like a flat back for shepards or stubby noses for pugs etc. Generally, "purebred" pets are far more prone to develop detrimental traits and illnesses, i don't see it worth the risk and more like torture than anything else.