Mendel used pea plants to conduct experiments demonstrating the inheritance of characters like height, colour, etc. When a tall plant was crossed with a dwarf plant, the progeny or first generation showed all tall plants. When two of these plants were crossed, the progeny showed three tall and one dwarf plant.

The above crosses show that only one T is enough to make the plant tall, that is, it dominates the inheritance of height. Thus, it is called the dominant trait. To make a plant dwarf, both the alleles must be t. Thus, it is the recessive trait.