How do Mendel's experiments show that traits are inherited independently?

Mendel crossed pea plants that had round, yellow seeds with plants that had wrinkled, green seeds. In the second generation, he got four combinations — not just the two parent types. This proved that seed shape and seed colour are passed on independently, not as a package.

Mendel demonstrated independent inheritance through his dihybrid cross experiment: 1. He crossed pure-breeding pea plants with round yellow seeds (RRYY) and wrinkled green seeds (rryy). 2. All F1 plants had round yellow seeds (RrYy), showing round and yellow are dominant traits. 3. He self-pollinated the F1 plants and observed the F2 generation. 4. The F2 generation produced four phenotypes in the ratio 9:3:3:1 — round yellow (9), round green (3), wrinkled yellow (3), wrinkled green (1). 5. If traits were inherited together (linked), only the two parental combinations would appear in F2. The appearance of new combinations (round-green and wrinkled-yellow) proved that the two traits segregate independently during gamete formation. This is Mendel's Law of Independent Assortment.