What did Gregor Mendel determine about inheritance?
That specific, individual traits could be passed on from one generation to another. The prevalent idea at the time -- one held by Charles Darwin -- was that the breeding of two living thngs with different traits would result in a mixing of these two traits. For example, that breeding a white horse with a black horse would result in a spotted horse, or a grey one. Mendel was able to show that, instead, such breeding could result in only one such trait -- the dominant one -- being passed on to the next generation. This was a major breakthough in explaining how species develop, and Mendel's idea was published in a scientific journal of the time. Amazingly, it was then forgotten for almost forty years.