What he did
Gregor Mendel was a genetics scientist in the 1800s. Hes experiments where primarily on pea plants. Seeing what would happen if he to two different pea plants and cross bread them.
Pictures of Gregor Mendel
He only used pure Gg or Yy Plants. He crossed (Dominate) green and (Recessive) yellow peas to make the yellow peas then he crossed the yellow peas and got some green peas back.
Dominate - A trait (or gene) that will overshadow over another trait. This trait always "wins". This trait will always show up.
Recessive - Trait (or gene) that will be masked or covered up by a dominate trait.