Peas

He found, to his excitement, that in almost exactly one-quarter of the cases, the characteristics of the "lost grandparent"-the "recessive"-re-emerged. Thus dwarf pea mixed with a tall one might produce tall offspring in the first generation, but when these self-fertilized, they each gave rise to a dwarf plant from one in every four seeds. (Weinberg 30)

This idea of a one in four dwarf pea immediately reminded me of the punnet square. In this case, the second generation pea plants had the following genetics, BB, Bb,Bb,bb. The first three of these would have been the tall pea plants that the monk, Gregor Mendel, observed. The only plant with the recessive dwarf gene was the last one, bb. That 25% chance of a recessive, bb, gene was what inspired the idea of dominant and recessive genes and how they operate. This discovery sparked much of what we know today about genetics and DNA. Along with Watson and Cricks, Mendel is a father of genetics.
Peas

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