Three independently assorting genes (A, B, and C) are known to control the following biochemical pathway that provides the basis for flower color in a hypothetical plant: Three homozygous recessive mutations are also known, each of which interrupts a different one of these steps. Determine the phenotypic results in the F₁ and F₂ generations resulting from the P₁ crosses of true-breeding plants listed here: colorless (aaBBCC) × green (AABBcc)

Key Concepts

Independent Assortment

Independent assortment is a fundamental principle of genetics stating that alleles for different genes segregate independently of one another during gamete formation. This means that the inheritance of one trait will not affect the inheritance of another trait, allowing for a variety of combinations in offspring. In the context of the question, it implies that the genes A, B, and C will assort independently when determining the phenotypes of the F₁ and F₂ generations.

Homozygous and Heterozygous Genotypes

A homozygous genotype consists of two identical alleles for a particular gene, while a heterozygous genotype contains two different alleles. In the given cross, the parental plants are homozygous for their respective traits (aaBBCC and AABBcc), which will produce heterozygous offspring (AaBbCc) in the F₁ generation. Understanding these genotypes is crucial for predicting the phenotypic ratios in subsequent generations.

Phenotypic Ratios in Genetic Crosses

Phenotypic ratios refer to the relative frequencies of different phenotypes in the offspring resulting from a genetic cross. In this scenario, the F₁ generation will display a uniform phenotype due to the dominance of the A allele, while the F₂ generation will exhibit a variety of phenotypes based on the combinations of alleles inherited. Analyzing these ratios helps in understanding the expression of traits influenced by the genes involved.