What is the predicted phenotypic ratio in the F2 generation due to the law of independent assortment?

• A. 3:1
• B. 1:1
• C. 9:3:3:1
• D. 4:1

Answer: (C)

The predicted phenotypic ratio in the F2 generation resulting from the law of independent assortment is 9:3:3:1, which is characteristic of a dihybrid cross involving two traits that assort independently. When considering two trait inheritance, each trait is controlled by different genes that segregate independently during gamete formation, according to Mendel's law of independent assortment.

In a classic dihybrid cross, taking sweet pea plants as an example, if we consider two traits such as seed shape (round vs. wrinkled) and seed color (yellow vs. green), the F1 generation typically exhibits the dominant phenotype for both traits. When these F1 individuals are crossed, the resulting F2 generation exhibits a phenotypic ratio that emerges from all possible combinations of the alleles.

Each trait contributes to a fraction of the offspring, leading to the specific ratios for each phenotype combination in the F2 generation. The 9:3:3:1 ratio reflects the following breakdown: 9 individuals have both dominant traits, 3 have the dominant trait for the first and recessive for the second, another 3 have the recessive trait for the first and dominant for the second, and 1 has both recessive traits