One of Mendel’s most revolutionary insights was that the combinations of Merkmale were essentially random. Four kinds of germ cells were available for mixing—A pollen, a pollen, A egg, and a egg—and each had an equal chance of joining with each of the others. The A pollen was just as likely to pair with the A egg as with the a egg; similarly, the a pollen had an equal chance of pairing with an egg from either A or a. Mendel’s calculations allowed him to go one step beyond his simple 3:1 ratio. When he thought through how the next year’s peas would look, he understood that among the F2 peas
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