Gregor Mendel learned through studies with pea plants that factors, now known as genes, are what determine biological inheritance. When he bred the plants, he noticed that the flower's color was never a blend of the parent plants' colors but rather a solid shade.
The genes that the plant offspring received determined the color of its flowers. A plant with one dominant gene exhibits that trait, while two copies of a recessive gene are required.
Mendel discovered that the alleles for the factors were passed from the parents to the children, with one allele coming from each parent. The combination of the alleles dictates which traits are exhibited.