If a breeder wanted to discover whether a black guinea pig was homozygous (BB) or heterozygous (Bb) for coat color, the animal in question could be crossed with an individual with what phenotype?

Answer 1

Whatever bb stands for, that is the one you would use as a mate. If the Black guinea pig was Bb, about half of the offspring would show the b phenotype — whatever that is. If BB, all of the offspring would be black.

You can verify this by using the Punnett square.

http://en.wikipedia.org/wiki/Punnett_square
http://anthro.palomar.edu/mendel/mendel_2.htm

I hope this helps. Thanks for asking.

Answer 2

BB