Initial results of Gregor Mendel’s monohybrid experiment on seed form or shape (round- x wrinkled-seeded parents) showed that the cross-fertilized garden peas (F1, his ‘hybrid’) exhibited only one character (he called it dominant) of either parent, that is, the round seededness.
He likewise found that the other parental character (wrinkled seeds) is only hidden in the F1 but reappeared in the F2 and in the succeeding generations.
He called this character recessive.
This observation was also true to the six other sets of characters that he investigated.
He demonstrated that the F2 progeny consisted of two phenotypic types: the dominants and the recessives.
The dominants are those which exhibit the dominant character only while the recessives are those which exhibit the recessive character only.
They occurred in the average proportion of 3:1.
Thus, as to seed shape, 3 were round-seeded and 1 was wrinkled-seeded in every four.
But he did not stop right there.
He proceeded further and made more discoveries.
He continued growing pea plants using seeds harvested in each generation and properly recorded his observations.
Since garden pea is a naturally self-pollinated plant, the next progenies (example F2) are largely selfed progenies of the next preceding generation (i.e., F1).