How did Gregor Mendel use the 3-to-1 ratio in pea plants?

Gregor Mendel used the 3-to-1 ratio as quantitative evidence to deduce the fundamental rules of heredity. By crossing pure-breeding pea plants with contrasting traits (such as yellow versus green seeds), he observed that the first generation (F1) displayed only the dominant trait.12

When he allowed these F1 hybrids to self-pollinate, the recessive trait reappeared in the second generation (F2) in a consistent proportion: approximately 3/4 of the plants exhibited the dominant trait and 1/4 showed the recessive trait.1

Mendel concluded from this 3-to-1 ratio that:
* Hereditary units, later called genes, exist in pairs within the plant.12
* These pairs separate during the formation of gametes, a concept known as the law of segregation.1
* The traits do not blend; rather, the recessive allele remains hidden in the F1 generation and segregates independently to reappear in the F2 generation.12