In F0, we have two blacks guinea pigs this tells us that they have at least one allele for the color black (B).
In F1, they tell us that everyone is black, so everyone also has the allele for the color black (B).
In F2, they tell us that there are 1/4 whites, which means that there is a second possibility of color, recessive (w).
The only way for a second allele to appear is that these characteristics are heterozygous. If you draw Punnett's square(photo) you'll find:
a)
F0: BB x Bw = BB BB Bw Bw= 4/4 black
F1: Bw x Bw = BB Bw Bw ww= 3/4 black 1/4 white.
White guinea pigs: ww
b)
If you cross two white Guinea pigs, you only have the recessive allele, so all of the offspring will be also white.
