Questions: When a 9:3:3:1 ratio of phenotypes is produced by a cross between two individuals, which phenotypes are present in the rarest class that is represented by only 1 of the 16 possible genotypes of offspring? These offspring have the recessive phenotype of both traits. These offspring have the dominant phenotype of one trait and the recessive phenotype of the other trait. These offspring have the dominant phenotype of both traits.

The answer is: The offspring with the recessive phenotype for both traits.

Explanation:

1. Understanding the 9:3:3:1 Ratio: This ratio is typical of a dihybrid cross, where two heterozygous individuals (AaBb x AaBb) are crossed. The ratio represents the phenotypic distribution of the offspring:

   • 9 offspring with both dominant traits (A-B-)
   • 3 offspring with the dominant trait for the first gene and recessive for the second (A-bb)
   • 3 offspring with the recessive trait for the first gene and dominant for the second (aaB-)
   • 1 offspring with both recessive traits (aabb)

2. Identifying the Rarest Class: The rarest class in this ratio is the one represented by the "1" in the 9:3:3:1 ratio. This corresponds to the offspring that are homozygous recessive for both traits (aabb).

3. Phenotypes of the Rarest Class: These offspring will exhibit the recessive phenotype for both traits, as they have the genotype aabb.

In summary, the rarest class in a 9:3:3:1 phenotypic ratio from a dihybrid cross is the offspring with the recessive phenotype for both traits.