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.

If strains G₂ and G₃ are crossed, what will be the phenotype of the F₁? 

Verified step by step guidance

1. Step 1: Analyze the table provided. The F1 phenotype for all crosses (G1 × Y, G2 × Y, G3 × Y) is 'All yellow,' indicating that yellow is dominant over green in these strains.
2. Step 2: Examine the F2 phenotypes for each strain. The proportions of green and yellow seeds differ among G1, G2, and G3, suggesting that different genetic mechanisms are responsible for the green phenotype in each strain.
3. Step 3: Note that G2 and G3 have different F2 ratios (7/16 green and 9/16 yellow for G2; 37/64 green and 27/64 yellow for G3). This indicates that the green phenotype in G2 and G3 is controlled by different sets of genes or alleles.
4. Step 4: When G2 and G3 are crossed, the F1 generation will inherit one allele from G2 and one allele from G3. Since the green phenotype is controlled by different genetic mechanisms in these strains, the F1 phenotype will likely be yellow due to the dominance of yellow alleles.
5. Step 5: To confirm this, consider that the F1 generation will be heterozygous for the alleles from G2 and G3. The dominance of yellow in both strains suggests that the F1 phenotype will be yellow regardless of the genetic differences between G2 and G3.

Key Concepts

Phenotype and Genotype

Phenotype refers to the observable characteristics of an organism, such as seed color in lentils, while genotype refers to the genetic makeup that determines these traits. In this case, the green-seeded strains (G₁, G₂, G₃) exhibit the same phenotype but may have different genotypes, which can affect the inheritance patterns observed in the F₂ generation.

Mendelian Inheritance

Mendelian inheritance describes the patterns of inheritance first outlined by Gregor Mendel, particularly the principles of dominance and segregation. In this scenario, the yellow seed trait is dominant over the green seed trait, leading to all F₁ offspring being yellow when crossed with a pure-breeding yellow strain. The F₂ generation reveals the segregation of traits, allowing for the calculation of phenotypic ratios.

F₁ and F₂ Generations

The F₁ generation is the first filial generation resulting from a cross between two parental strains, while the F₂ generation is produced by self-fertilization of the F₁ plants. The phenotypic ratios observed in the F₂ generation provide insights into the genetic relationships and dominance of traits, as seen in the varying proportions of green and yellow seeds from the different green-seeded strains.