Final answer:
A Punnett square of a cross between two heterozygous (Bb) black guinea pigs predicts a phenotypic ratio of 3 black : 1 white. Each Bb parent contributes the B or b allele, resulting in possible offspring genotypes of BB, Bb, bb, and the same Bb heterozygous genotype.
Step-by-step explanation:
In biology, a Punnett square is a chart that is used to predict the result of a particular cross or breeding experiment. It is named after Reginald C. Punnett, who devised the approach. The question describes a cross between two heterozygous black guinea pigs, which in genetic terms are represented as Bb (B for the dominant black allele and b for the recessive white allele). When creating a Punnett square for the cross between two heterozygous organisms (Bb x Bb), you’ll see that four possible combinations can result: BB, Bb, bB, and bb. Here, both Bb and bB represent the same genotype - heterozygous black, since the order of the alleles does not affect the phenotype.
The expected outcome is that
- BB (homozygous dominant) would lead to black coat offspring,
- Bb and bB (heterozygous) would also lead to black coat offspring due to black being dominant, and
- bb (homozygous recessive) would lead to white coat offspring.
As a result, the phenotypic ratio of the coat color in the offspring from this cross would likely be 3 black : 1 white. This follows Mendelian principles of inheritance. If we compare to a similar situation in mice, where certain genes are responsible for coat color and others for epistasis, we can draw parallels on how dominant and recessive genes interact across different species.