Monohybrid Crosses And The Punnett Square Lesson Plan Template (Page 3 of 4) in pdf

Name ________________________

Monohybrid Crosses and the Punnett Square

Introduction

Scientists use a grid-like tool (Punnett Square) to make predictions about various genetic problems. The

Punnett Square shows only the probability of what might occur and not the actual results. Probability is the

chance of something occurring. If one wants to flip a coin 100 times, since there are 2 sides to the coin, he

would expect 50 heads and 50 tails. If he flips the coin 100 times, he may actually get 60 heads and 40 tails.

Prediction is one thing, and actually getting the predicted results is another. The Punnett Square only shows the

chances of what might occur each time the event is undertaken.

Objective

In this investigation, you will use a Punnett Square to predict the possible genotypes and phenotypes and their

ratios from a monohybrid cross.

Pre-lab questions

Define the following terms:

1. Punnett square - ______________________________________________________________________

2. genotype - ___________________________________________________________________________

3. phenotype - __________________________________________________________________________

4. homozygous - ________________________________________________________________________

5. heterozygous - _______________________________________________________________________

6. trait - _______________________________________________________________________________

7. dominant - __________________________________________________________________________

8. recessive - ___________________________________________________________________________

Materials

• red beans

• white beans

• 2 small paper bags (one labeled male and the other labeled female)

Procedure

1. Each group of 2 students will pick up 2 paper bags filled with 15 red (R) beans and 15 white (r) beans. This

represents 2 heterozygous parents (Rr x Rr).

2. One student in the group will be in charge of the male bag and the other student will be in charge of the

female bag.

3. At the same time, each student will reach into their bag and pull out one of the beans. The only possibilities

that can be made from this selection are: RR (homozygous red), Rr (heterozygous red), or rr (homozygous

white). Mark the resulting genotype and phenotype in the data table.

4. Return the beans back into the bag and conduct the same process 14 more times (15 total trials).

Monohybrid Crosses And The Punnett Square Lesson Plan Template Page 3