The genes for the traits that Mendel worked with are either all located on different chromosomes or behave as if they were. How did this help Mendel recognize the principle of independent assortment? a. Otherwise, his dihybrid crosses would not have produced a 9 : 3 : 3 : 1 ratio of F2 phenotypes. b. The occurrence of individuals with unexpected phenotypes led him to the discovery of recombination. c. It led him to the realization that the behavior of chromosomes during meiosis explained his results. d. It meant that the alleles involved were either dominant or recessive, which gave 3 : 1 ratios in the F1 generation.

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1. Mendel's genes being on different chromosomes or behaving as if they were allowed each pair of alleles to segregate independently during gamete formation.
2. This independent assortment during meiosis meant that all possible combinations of alleles could occur in the gametes.
3. In dihybrid crosses, this independent assortment results in the production of gametes with all combinations of traits from the parental generation.
4. When these gametes combine during fertilization, they produce offspring with a variety of combinations of traits, leading to the 9:3:3:1 phenotypic ratio observed in the F2 generation.
5. Thus, the correct answer is: a. Otherwise, his dihybrid crosses would not have produced a 9 : 3 : 3 : 1 ratio of F2 phenotypes.