My firm is an investor in Embark (https://embarkvet.com/), whichh is basically 23 & Me for Mastiffs. If you want to understand the delightful world of doggy DNA, there is no better destination.
I hope these services can one day remove the one downside to pure breeds — inbred health issues. It would be amazing to have a near guarantee on dog temperament without, say, hip displasia.