A plant line with reduced fertility comes to the attention of a plant breeder who observes that seed pods often contain a mixture of viable seeds that can be planted to produce new plants and withered seeds that cannot be sprouted. The breeder examines numerous seed pods in the reduced fertility line and counts 622 viable seeds and 204 nonviable seeds.

What single-gene mechanism best explains the breeder's observation?

Key Concepts

Mendelian Inheritance

Mendelian inheritance refers to the principles of heredity established by Gregor Mendel, which describe how traits are passed from parents to offspring through discrete units called genes. In this context, the observation of viable and nonviable seeds suggests a single-gene trait, where one allele may be dominant and responsible for seed viability, while a recessive allele leads to nonviable seeds.

Genetic Ratio

The genetic ratio is a way to express the expected proportions of different genotypes or phenotypes resulting from a genetic cross. In this case, the ratio of viable to nonviable seeds (622:204) can be simplified to approximately 3:1, which is characteristic of a monohybrid cross involving a single gene with dominant and recessive alleles.

Allelic Interaction

Allelic interaction refers to how different alleles of a gene influence the phenotype of an organism. In the scenario presented, the presence of both viable and nonviable seeds indicates that the plant line may carry one allele for viability and another for nonviability, leading to a phenotypic expression that reflects the dominance of the viable allele over the nonviable one.