Final answer:
Yes. It is possible for two black guinea pigs to not produce a white offspring, especially if both are homozygous for the black color gene (BB). If both are heterozygous (Bb), a white offspring (bb) could occur. The phenomenon of epistasis can also result in different color outcomes, even producing albinos.
Step-by-step explanation:
Yes, it is possible that a cross between two black guinea pigs would not produce a white guinea pig when using a Punnett Square. This could occur if both black guinea pigs are homozygous dominant (BB) for the black color trait, as this would mean they do not carry the allele for the white color. If we use the letters 'B' for the dominant black-colored allele and 'b' for the recessive white-colored allele in a Punnett Square, and both parents are BB, all offspring would also be BB (black).
However, if the two black guinea pigs are each carrying one copy of the white allele (being Bb),
In this case, the possible offspring genotypes would be 25% BB (black), 50% Bb (black), and 25% bb (white).
This demonstrates that the black guinea pigs can produce a white offspring if they are both heterozygous for the trait.
Furthermore, epistasis could also play a role.
Epistasis occurs when the expression of one gene is affected by another gene.
For example, if a gene that is necessary for pigment production is not present (cc), the animal will be albino regardless of other color genes present.
Therefore, a cross between heterozygotes for both a pigment gene and a color gene (AaCc x AaCc) could result in a variety of phenotypes including an albino one, which would be white in appearance.