Blue moon beans produce beans that are either the dominant color blue or the recessive color white. The bean pods for this species always contain four seeds each. If two heterozygous plants that each have the Bb genotype are crossed, what are the predicted frequencies of each of the five outcome classes for combinations of blue and white seeds in pods?

Key Concepts

Mendelian Genetics

Mendelian genetics is the study of how traits are inherited through generations based on the principles established by Gregor Mendel. It involves understanding dominant and recessive alleles, where dominant alleles mask the expression of recessive ones. In this case, the blue color (B) is dominant over the white color (b), which is crucial for predicting the offspring's phenotypes.

Punnett Square

A Punnett square is a diagram used to predict the genotypic and phenotypic outcomes of a genetic cross. By arranging the alleles of the parents along the top and side of a grid, one can visualize all possible combinations of alleles in the offspring. For the Bb x Bb cross, the Punnett square helps determine the expected ratios of blue and white seeds in the resulting pods.

Genotypic and Phenotypic Ratios

Genotypic ratios refer to the relative frequencies of different genotypes in the offspring, while phenotypic ratios refer to the observable traits. In the case of the Bb x Bb cross, the genotypic ratio is 1 BB : 2 Bb : 1 bb, leading to a phenotypic ratio of 3 blue (BB and Bb) to 1 white (bb). Understanding these ratios is essential for predicting the outcomes of genetic crosses.