hey my friend did this one on Answer.com
Whenever Mendel performed a cross with pea plants, he carefully categorized and counted the many offspring. Every time Mendel repeated a particular cross, obtained similar results. For example, whenever Mendel crossed two plants that were hybrid for stem height (Tt), about three fourths of the resulting plants were tall and about one fourth were short. Mendel realized that the principles of probability could be used to explain the results of genetic crosses.