Let a dog with ‘black colour homozygous trait (BB)’ mate with dog with ‘white homozygous trait (bb)’. If the offspring of Ft generation are black, then the black trait is dominant. If the offspring of F₁ generation are all white, then the white trait is dominant.

Male dog with x Female dog with

white coat colour   black coat colour

    WW                  bb

               ↓

   Wb Wb Wb  Wb 

All white offspring → F₁

F₁ x F₁ → Male dog x Female dog

               Wb              Wb

                                  ↓

                     WW Wb Wb   bb → F₂

                     white white white white