Three strains of green-seeded lentil plants appear to have the same phenotype. The strains are designated G₁, G₂, and G₃. Each green-seeded strain is crossed to a pure-breeding yellow-seeded strain designated Y. The F₁ of each cross are yellow; however, self-fertilization of F₁ plants produces F₂ with different proportions of yellow- and green-seeded plants as shown below.

What proportion of the F₂ are expected to be green? Show your work. 

Verified step by step guidance

1. Step 1: Analyze the table provided. The table shows the F1 phenotype (all yellow) and the F2 phenotype proportions for green and yellow seeds for three strains (G1, G2, G3) crossed with a pure-breeding yellow strain (Y).
2. Step 2: Recognize that the F1 generation being all yellow indicates that yellow is dominant over green. This suggests that the green-seeded strains (G1, G2, G3) are heterozygous or involve different genetic mechanisms.
3. Step 3: For the F2 generation, the proportions of green and yellow seeds differ among the strains. Use the proportions provided in the table to infer the genetic ratios. For example, G1 shows a 1:3 ratio (1/4 green, 3/4 yellow), which corresponds to a single-gene Mendelian inheritance pattern with heterozygous parents (Aa x Aa).
4. Step 4: For G2, the F2 proportions (7/16 green, 9/16 yellow) suggest a dihybrid cross involving two genes with epistasis or interaction between genes. This ratio aligns with a modified Mendelian dihybrid ratio.
5. Step 5: For G3, the F2 proportions (37/64 green, 27/64 yellow) indicate a more complex genetic interaction, possibly involving multiple genes or incomplete dominance. To calculate the expected proportion of green seeds, use the ratios provided in the table directly for each strain.

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 context, the yellow seed trait is dominant over the green seed trait. When green-seeded strains are crossed with a pure-breeding yellow strain, the F1 generation exhibits the dominant phenotype, while the F2 generation reveals the segregation of traits according to Mendel's laws.

Phenotypic Ratios

Phenotypic ratios describe the relative frequencies of different phenotypes in a given generation. In the F2 generation, the expected ratios can be calculated based on the genotypes of the parents. For example, a typical monohybrid cross results in a 3:1 ratio of dominant to recessive phenotypes, but variations can occur depending on the genetic makeup of the strains involved, as seen in the F2 results for G1, G2, and G3.

Self-Fertilization

Self-fertilization is the process by which a plant fertilizes itself, leading to the production of offspring that may exhibit a range of phenotypes. In this scenario, the F1 plants, which are all yellow, are self-fertilized to produce the F2 generation. The resulting proportions of green and yellow seeds in the F2 generation provide insights into the underlying genetic mechanisms and the segregation of alleles.