Question

In dalmatians, the gene for black spots (B) is dominant to the gene for liver spots (b). A dalmatian with genotype (Bb) was crossed with a dalmatian with genotype (bb), as shown in the Punnett square.


Dalmatian with black spots Dalmatian with liver spots
What fraction of the offspring should be expected to have black spots?

Answer 1

Cross Bb × bb. Gametes: Bb gives B or b; bb gives b only.

Punnett square:
- B × b → Bb (black)
- b × b → bb (liver)

So 1 out of 2 (1/2) of the offspring, or 50%, are expected to have black spots.