Question

Two true-breeding pea plants are crossed. One parent is round, terminal, violet, constricted, while the other expresses the contrasting phenotypes of wrinkled, axial, white, full. The four pairs of contrasting traits are controlled by four genes, each located on a separate chromosome. In the F₁ generation, only round, axial, violet, and full are expressed. In the F₂generation, all possible combinations of these traits are expressed in ratios consistent with Mendelian inheritance.
What conclusion can you draw about the inheritance of these traits based on the F₁ results?

Accepted Answer

Identify the parental genotypes based on the given phenotypes. Since the parents are true-breeding, one parent is homozygous for round, terminal, violet, and constricted traits, and the other is homozygous for wrinkled, axial, white, and full traits. Determine the dominant and recessive traits by examining the F\_1 generation phenotypes. The F\_1 plants express round, axial, violet, and full traits, indicating these are the dominant phenotypes. Write the genotype of the F\_1 generation as heterozygous for all four genes, since they inherit one allele from each parent. For example, if R = round (dominant) and r = wrinkled (recessive), then the F\_1 genotype for that gene is Rr. Understand that the expression of only the dominant traits in the F\_1 generation suggests simple Mendelian dominance for each gene, with no gene interactions or linkage affecting these traits. Conclude that each trait is inherited independently and follows Mendel's law of dominance, where the dominant allele masks the recessive allele in the heterozygous F\_1 individuals.

Key Concepts

Mendelian Inheritance

Dominance and Recessiveness

Independent Assortment