Step 1: Understanding the Question:
The question asks for the observable physical ratio (phenotypic ratio) of offspring in the second filial generation (\(F_2\)) when two traits are tracked simultaneously, following Mendel's Law of Independent Assortment.
Step 2: Detailed Explanation:
In a dihybrid cross (e.g., crossing RRYY - Round Yellow with rryy - Wrinkled Green):
1. The \(F_1\) generation is \(RrYy\) (all Round Yellow).
2. Selfing \(F_1\) (\(RrYy \times RrYy\)) produces a \(4 \times 4\) Punnett square with 16 combinations.
The resulting phenotypes are:
- 9 Round, Yellow (Both dominant traits)
- 3 Round, Green (One dominant, one recessive)
- 3 Wrinkled, Yellow (One recessive, one dominant)
- 1 Wrinkled, Green (Both recessive traits)
Thus, the ratio is \(9:3:3:1\).
Step 3: Final Answer:
The phenotypic ratio is \(9:3:3:1\).