Final answer:
Mendel's Law of Independent Assortment is the principle describing how genes for different traits segregate independently during gamete formation, which is demonstrated in dihybrid crosses resulting in a variety of genotypic combinations in offspring.
Step-by-step explanation:
The principle that Mendel discovered, which states that genes for different traits can segregate independently during the formation of gametes, is known as Mendel's Law of Independent Assortment. This law means that the allele pairs separate independently during the production of gametes, leading to the inheritance of one trait being generally unaffected by the inheritance of another. This law is best demonstrated through dihybrid crosses, wherein the inheritance of two traits is observed, typically resulting in a 9:3:3:1 ratio in the F2 generation for plants that are heterozygous for both traits.
For example, considering two pea plants, one with green, wrinkled seeds (yyrr) and the other with yellow, round seeds (YYRR), their gamete formation illustrates the law. The gametes for the green, wrinkled plant are all 'yr', while the gametes for the yellow, round plant are all 'YR', resulting in F1 generation offspring that are all 'YyRr'. This exemplifies that the gene for seed color is sorted independently from the gene for seed texture.
It explains that different genes separate independently of one another when forming gametes, contributing to genetic variation.