Two pure-breeding wheat strains, one producing dark red kernels and the other producing white kernels, are crossed to produce F₁ with pink kernel color. When an F₁ plant is self-fertilized and its seed collected and planted, the resulting F₂ consist of 160 plants with kernel colors as shown in the following table. Kernel Color Number White   9 Dark red 12 Red 39 Light pink 41 Pink 59 How many additive alleles are required to explain the five phenotypes seen in the F₂?

Key Concepts

Additive Alleles

Additive alleles refer to multiple alleles that contribute to a single trait in a cumulative manner. In the context of kernel color in wheat, each allele can influence the intensity or shade of the color produced. The presence of different combinations of these alleles results in a range of phenotypes, demonstrating how traits can be expressed in a continuous spectrum rather than as discrete categories.

Phenotypic Ratio

Phenotypic ratio is the relative frequency of different phenotypes in the offspring of a genetic cross. In this case, the F₂ generation shows a variety of kernel colors, which can be analyzed to determine the underlying genetic mechanisms. Understanding the phenotypic ratio helps in predicting the inheritance patterns and the number of alleles involved in producing the observed traits.

Self-Fertilization and Generational Analysis

Self-fertilization is the process where a plant fertilizes itself, leading to the next generation, or filial generation (F₂). Analyzing the offspring from self-fertilized F₁ plants allows geneticists to observe the segregation of traits and infer the number of alleles involved. This analysis is crucial for understanding inheritance patterns and the genetic basis of the observed phenotypes.