How do Mendel's experiments show that traits may be dominant or recessive and that traits are inherited independently?

Mendel's experiments with pea plants demonstrated both the concepts of dominant and recessive traits and independent assortment.

Dominant and Recessive Traits: Mendel crossed pea plants with contrasting traits, such as flower color (purple vs. white). In the first filial (F1) generation, all plants exhibited the dominant trait (purple flowers). However, when he crossed the F1 generation plants, the recessive trait (white flowers) reappeared in the F2 generation in a predictable ratio (approximately 3:1 purple to white). This demonstrated that the white flower trait, although masked in the F1 generation, was not lost but simply recessive to the purple flower trait. The reappearance of the white flower trait in the F2 generation showed that both traits (purple and white) were present in the F1 generation, but only the dominant one was expressed. This explained the inheritance pattern of single traits.

Independent Assortment: To demonstrate independent assortment, Mendel performed dihybrid crosses, tracking two different traits simultaneously. For example, he crossed plants with round, yellow peas (dominant traits) with plants with wrinkled, green peas (recessive traits). The F1 generation exhibited only round, yellow peas. The crucial observation came from the F2 generation. Instead of getting only round, yellow peas or wrinkled, green peas, he observed a variety of combinations in a specific ratio (approximately 9:3:3:1). The 9:3:3:1 ratio indicated that the traits for pea shape and pea color were inherited independently of each other. The inheritance of one trait (shape) did not influence the inheritance of the other (color). This principle is essential because it means that different traits are sorted into gametes (sex cells) independently of each other during meiosis. This independent assortment generates genetic variation in offspring, contributing to the diversity found in sexually reproducing organisms.