In guinea pigs, black coat colour (B) is dominant over white (b), and short hair length (H) is dominant over long (h). Indicate the genotypes and phenotypes from the following crosses:

Question

anonymous · Answer

a) A guinea pig that is homozygous for black and heterozygous for short hair is crossed with a white, long-haired guinea pig.

b) A guinea pig that is heterozygous for black and for short hair is crossed with a white, long-haired guinea pig.

c) A guinea pig that is homozygous for black and for long hair is crossed with a guinea pig that is heterozygous for black and for short hair.

anonymous · Answer

Heeeelp! I don't understand!! D;

turingtest · Answer

a) A guinea pig that is homozygous for black and heterozygous for short hair is crossed with a white, long-haired guinea pig.

let's just look at color first. Homozygous means the same copy of the gene. 
we are told one guinea pig is homozygous for black (BB). Since white hair is recessive, that means a white-haired guinea pig is homozygous for white (bb)
Here's how we do (BB)x(bb):|dw:1321488781531:dw|
so it looks like (BB)x(bb)=%100(Bb) so all offspring will have the black hair phenotype, because black is dominant...