A true-breeding pea plant with round, green seeds was crossed to a true-breeding plant with wrinkled, yellow seeds. Round and yellow are dominant traits. The F1 plants were allowed to self-fertilize.

What are the following probabilities for the F2 generation?

1. An F2 plant with wrinkled, yellow seeds.

2. All three F2 plants have round, yellow seeds.

3. Five F2 plants in the following order: two have round, yellow seeds; one has round, green seeds; and two have wrinkled, green seeds.

4. An F2 plant will not have round, yellow seeds.

Be sure to show your work clearly and concisely. A simple number for the answer does not communicate your understanding clearly

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Explanation:

Gregor Mendel developed the model of heredity that now bears his name by experiments on various charactersitics of pea plants: height (tall vs. Short); seed color (yellow vs. Green); seat coat (smooth vs. wrinkled), etc. The following explanation uses the tall/short trait. The other traits Mendel studied can be substituted for tall and short.

Mendel started out with plants that "bred true". That is, when tall plants were self-pollinated (or cross-pollinated with others like them), plants in following generations were all tall; when the short plants were self-pollinated (or cross- pollinated with others like them) the plants in following generations were all short.

Mendel found that if true breeding Tall [T] plants are crossed (bred) with true breeding short [t] plants, all the next generation of plants, called F1, are all tall.

Next, he showed that self-pollinated F1 plants (or cross- pollinated with other F1 plants) produce an F2 generation with 3/4 of the plants tall and 1/4 short.

A. 1/4 of the F2 generation are short plants, which produce only short plants in the F3 generation, if they are self- pollinated (or crossed with other short F2 plants;) these F2 plants breed true.

B, 1/4 of the F2 generation (1/3 of the tall plants) are tall plants that produce only tall plants in the F3 generation, if they are self-pollinated; these tall F2 plants breed true.

C. 1/2 of the F2 generation (2/3 of the tall plants) are tall plants that produce 1/4 short plants and 3/4 tall plants in the next [F3] generation, if they are self-pollinated. This is the same proportion of tall to short that F1 plants produce.