What is the required parental genotypes to produce a 3:1 ratio of phenotypes in offspring?

To achieve a 3:1 ratio of phenotypes in the offspring, the appropriate parental genotypes must allow for a combination of dominant and recessive traits. The Bb x Bb combination consists of two heterozygous parents, where each parent has one dominant allele (B) and one recessive allele (b).

When two heterozygous parents breed, the genotypes of the offspring can be calculated using a Punnett square, which would yield the following combinations: BB, Bb, Bb, and bb. This results in three offspring exhibiting the dominant phenotype (BB and Bb) and one offspring exhibiting the recessive phenotype (bb), which translates into a phenotypic ratio of 3 dominant to 1 recessive.

In contrast, other combinations do not produce this desired ratio. For example, BB x bb would yield only dominant phenotypes, and Bb x bb would result in a 1:1 ratio of dominant and recessive phenotypes. GG x gg would similarly not produce a 3:1 ratio, as the alleles do not allow for the necessary combinations to manifest both phenotypes in the expected proportions. Thus, the Bb x Bb genotype combination is the only one that leads to the expected 3:1 ratio