* Traits appear in predictable ratios: When Mendel crossed pea plants with different traits (like flower color), he didn't get a blend of the traits. Instead, the offspring consistently showed one trait or the other in predictable ratios. This suggested that something was being passed down in discrete units, not blending together.
* Recessive traits reappear: When Mendel crossed offspring with the dominant trait, he occasionally saw the recessive trait reappear in the next generation. This indicated that the recessive trait wasn't lost, but simply masked by the dominant trait.
* The Law of Segregation: Based on his observations, Mendel proposed the Law of Segregation. This law states that each individual has two copies of each gene (one from each parent), and these copies separate during gamete formation (sperm and egg), so each gamete only receives one copy.
Mendel's model was revolutionary: Before Mendel, people thought traits were blended. His work revealed that inheritance worked through discrete units (which we now call genes), and these units were inherited in pairs. This laid the foundation for modern genetics.
