A dark-red strain and a white strain of wheat are crossed and produce an intermediate, medium-red F₁. When the F₁ plants are interbred, an F₂ generation is produced in a ratio of 1 dark-red: 4 medium-dark-red: 6 medium-red: 4 light-red: 1 white. Further crosses reveal that the dark-red and white F₂ plants are true breeding

Assign symbols to these alleles, and list possible genotypes that give rise to the medium-red and light-red phenotypes.

Key Concepts

Incomplete Dominance

Incomplete dominance occurs when the phenotype of heterozygous individuals is intermediate between the phenotypes of the two homozygous parents. In this case, crossing a dark-red strain with a white strain results in an F₁ generation that exhibits a medium-red phenotype, demonstrating that neither allele is completely dominant over the other.

Genotype and Phenotype Relationship

The genotype refers to the genetic makeup of an organism, while the phenotype is the observable expression of that genotype. In this scenario, the medium-red and light-red phenotypes arise from specific combinations of alleles, which can be represented as genotypes. Understanding this relationship is crucial for predicting the phenotypic outcomes of genetic crosses.

Punnett Square and Ratios

A Punnett square is a tool used to predict the genotypic and phenotypic ratios of offspring from a genetic cross. The given F₂ generation ratio of 1 dark-red: 4 medium-dark-red: 6 medium-red: 4 light-red: 1 white can be analyzed using a Punnett square to determine the possible genotypes that correspond to each phenotype, aiding in the assignment of allele symbols.