During the second half of the 19th century, directed crossings were a usual practice to study inheritance. Many researchers were unable to reach the same Mendel conclusions since they did not use the appropriate biological material or the appropriate methodology. Mendel used an excellent experimental design, with the following methodological advantages.

Selection of appropriate material.

He chose Pisum Sativum plants, which have the following advantages:

1. They produce several generations in a year.
2. Its flowers have the female reproductive system (pistil) and the male (stamen) enclosed within the corolla, which facilitates self-fertilization and prevents spontaneous crossing with pollen from other varieties, although in these plants it is easy to perform cross-fertilization, manually transporting the pollen from one flower to another;
3. They are simple enough to allow their manipulation and present clearly observable features.

Study of characters and specific features.

In his works, Mendel focused his attention on a single feature each time, and not on all the characteristics of the plant, as did other researchers of his time. He fixed his attention on seven specific and visible characters of the plant, represented by two contrasting features:

1. Size of the plant (tall or dwarf).
2. The texture of the seed (smooth or rough).
3. The color of the cotyledons of the seed (yellow or green).
4. The color of the seed coat (gray or white).
5. The position of the flowers on the stem (axial or terminal).
6. The shape of the pod (wide or narrow).
7. The color of the pod (green or yellow).