Mr. Jones has a black guinea pig. (In guinea a pig, black is dominant to white). He wants to know if the guinea pig is pure, because he wants to breed her and raise black guinea pigs to sell.
He brings the guinea pig to you. What would you tell Mr. Jones? What would you do? How would you interpret your results?

Based on the phenotypic assessment and test breeding results, I can confirm that Mr. Jones's guinea pig is purebred black if all offspring from the test breeding exhibit black coloring.

Explanation:

Upon examination of Mr. Jones's guinea pig, I will carefully analyze its coat color to determine if it expresses the dominant black allele. If the guinea pig displays black coloring, it suggests that it carries at least one dominant black allele, which is indicative of its potential to produce black offspring.

To further ascertain its genetic makeup, I would suggest a test breeding with a known genotype, such as a homozygous recessive white guinea pig. By observing the coat colors of the offspring, we can deduce whether the black guinea pig is homozygous dominant (BB) or heterozygous (Bb) for black coat color.

Upon analyzing the results of the test breeding, if all offspring exhibit black coloring, it confirms that the black guinea pig is homozygous dominant (BB) for black coat color.

This implies that it is purebred for black and will consistently produce black offspring when bred with another guinea pig. However, if any offspring display white coloring, it suggests that the black guinea pig is heterozygous (Bb) for black coat color, indicating that it carries one dominant black allele and one recessive white allele.

Therefore, based on the phenotypic assessment and test breeding results, I can conclusively inform Mr. Jones whether his guinea pig is purebred black and suitable for breeding to produce black offspring for sale.