Final answer:
In the biology subject, specifically genetics, the offspring of a dihybrid cross involving heterozygous plants with traits for height and pod shape follow a phenotypic ratio of 9:3:3:1, demonstrating the independent assortment of traits.
Step-by-step explanation:
The question asks about the offspring resulting from a dihybrid cross. A dihybrid cross involves organisms that are heterozygous for two traits. In this specific example, we are considering pea plants with two traits: plant height (tall or dwarf) and pod type (inflated or constricted). Assuming we are working with traits where tall and inflated are dominant over dwarf and constricted, when you cross a plant that is heterozygous for both traits (TtIi) with another TtIi plant, the offspring will follow a phenotypic ratio of 9:3:3:1. That is, 9 will show both dominant traits (tall and inflated pods), 3 will show the dominant trait for height and the recessive trait for pod type (tall and constricted pods), 3 will show the recessive trait for height and the dominant trait for pod type (dwarf and inflated pods), and 1 will have both recessive traits (dwarf and constricted pods).
Mendel's work, often conducted through such crosses, led to the formulation of what we now know as Mendelian genetics, the foundation of classical genetics. His experiments, including dihybrid crosses, demonstrated the independent assortment of traits.