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 consists of 160 plants with kernel colors as shown in the following table.

If an F₁ plant is crossed to a dark red plant, what are the expected progeny phenotypes, and what is the expected proportion of each phenotype?

Verified step by step guidance

1. Step 1: Understand the genetic basis of kernel color in wheat. The problem suggests that kernel color is controlled by multiple alleles, likely involving incomplete dominance or additive effects. The F₁ generation exhibits pink kernel color, which is intermediate between the dark red and white parental phenotypes, indicating incomplete dominance.
2. Step 2: Analyze the F₂ generation data. The phenotypic ratios in the F₂ generation (White: 9, Dark red: 12, Red: 39, Light pink: 41, Pink: 59) suggest that kernel color is influenced by two or more genes, each contributing to the phenotype. Assign genotypes to each phenotype based on the observed ratios and inheritance pattern.
3. Step 3: Determine the genetic makeup of the F₁ plant and the dark red plant. The F₁ plant is heterozygous for the alleles controlling kernel color, while the dark red plant is homozygous for the alleles producing the dark red phenotype. Represent these genotypes symbolically (e.g., AaBb for F₁ and AABB for dark red).
4. Step 4: Predict the progeny phenotypes and proportions when the F₁ plant is crossed with the dark red plant. Use a Punnett square to calculate the possible combinations of alleles in the offspring. Consider the contribution of each gene to the phenotype and the dominance relationships between alleles.
5. Step 5: Translate the genotypic combinations into phenotypic categories. Based on the inheritance pattern, assign phenotypes (e.g., dark red, red, pink, etc.) to each genotype and calculate the expected proportions of each phenotype in the progeny. Ensure the proportions align with Mendelian inheritance principles.

Key Concepts

Mendelian Inheritance

Mendelian inheritance refers to the principles of heredity established by Gregor Mendel, which include the concepts of dominant and recessive traits. In this scenario, the dark red kernel color is likely dominant over white, while pink is an intermediate phenotype. Understanding these principles helps predict the inheritance patterns of traits in offspring.

Phenotypic Ratios

Phenotypic ratios describe the relative frequencies of different phenotypes in the offspring of a genetic cross. In this case, the F₂ generation's phenotypic ratio can be analyzed to determine the expected proportions of each kernel color. This ratio is crucial for predicting the outcomes of further crosses, such as the F₁ crossed with a dark red plant.

Punnett Square

A Punnett square is a diagram used to predict the genotypes and phenotypes of offspring from a genetic cross. By mapping the alleles of the parents, one can visualize the potential combinations in the progeny. This tool is essential for calculating the expected proportions of each phenotype when crossing the F₁ plant with a dark red plant.