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Reginald Punnett was a British geneticist

1. Mendel observed that pea plants had traits, such as color, that were either “one or the other,” never something in between. In your own words, discuss the correlation between Mendel’s factors, what they might be, and why pea plant traits come in one form or another—e.g., gray or dark red—rather than blended.

2. In your own words, explain why all the offspring in the F1 generation were yellow instead of half being yellow and half green, or some other mix of the colors. Hint: Remember that Mendel coined the terms dominant and recessive.

3. Reginald Punnett was a British geneticist who developed the Punnett square to explain how the chromosomes of parents cross and produce offspring. In order to solve genetics problems using a Punnett square, it is necessary to a) understand the associated vocabulary and b) understand some of the rules for solving the problems.

4. Yellow seeds are dominant over green seeds in pea plants. Cross a heterozygous (yellow seeded) plant with a green seeded plant.

What is the genotypic ratio of the offspring in Question 4?

What is the phenotypic ratio of the offspring in Question 4?

5. Now cross two of the heterozygous F1 offspring from question #2.

What is the genotypic ratio of the offspring in Question 5?

What is the phenotypic ratio of the offspring in Question 5?

6. Consider the resulting ratio of crossing the two heterozygous pea plants in question #5.  We will use this ratio in a short activity exploring probability. Keep in mind that crossing two individuals that are heterozygous for a certain trait is similar to flipping two coins. Each coin has two sides (we might think of each side as an “allele”) and the chances of flipping heads/heads, heads/tails or tails/tails should be similar to the ratio we see when crossing two heterozygotes.

For this simple activity, you will need two coins (pennies, nickels, dimes, quarters, or a mix of any of those). Alternatively, you may google a coin-flipper simulator that will allow you to flip two coins at once. You will also need a piece of scratch paper and a pen or pencil.

Compare the resulting ratio from the question #5 cross of two heterozygous parents to the ratio from the coin flipping exercise. Are there similarities? If so, what are they?

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