Answer :
Mendelian inheritance was discovered when Gregor Mendel cross two pure breeds of peas. One is a pure breed of a purple pea plant and the other is a pure breed of a white pea plant. The result of the experiment is a hybrid offspring with violet flowers. The hybrid offspring is cross with each other and produce violet and white flowers.
For Mendel, it gave him the idea that there are "factors" affecting the inheritance of traits. These "factors" are now known as the genes, which are pairs of alleles that can have three genotypes: AA (homozygous dominant), aa (homozygous recessive), and Aa (heterozygous).
ANSWER:
In Mendel's experiment, the pure purple pea plant is homozygous dominant (PP) and the pure white pea plant is a homozygous recessive (pp). When they are crossed, the offspring become heterozygous/hybrid (Pp). Since the purple flower is dominant over the white flower based on their genotypes, the offspring will manifest a purple flower instead of a white flower.
But when two hybrid offspring are crossed, the produced offspring will either be purple or white. Thus, the "factors" can either be dominant or recessive.