Plant Genetics

Experiment 6: Plant Genetics

Abstract

Students will learn classic Mendelian Genetics and use a Punnett square to predict the outcome of genetic crosses. Students will perform a monohybrid cross using tobacco mosaic seeds and study a dihybrid cross using corn.

Introduction

This lab is done to predict the genetic frequency of offspring in a monohybrid cross, to predict the outcomes of genetic crosses using Punnett squares, and to statistically analyze the results of a genetic cross.

Materials:

Materials from: Label or box/bag QTY Item description

Student provides 1

1 Paper towel

Water

LabPaq provides 2

1

1 Seed, tobacco

Magnifier, dual

Petri dish, 90 mm

Procedure 1: Observing a Monohybrid Cross

Note: Plant the tobacco seeds 5-6 days before performing the rest of the experiment.

1. Cut a piece of paper towel to fit inside a Petri dish.

2. Place the paper towel inside the Petri dish and moisten with water.

3. Sprinkle all of the seeds onto the paper towel and then cover the Petri dish.

4. Place seeds near a warm window with indirect light.

5. Observe seeds for germination each day, and moisten the paper towel as needed.

Note: It will take 5-6 days for the seeds in this exercise to germinate.

6. Create a Punnett square (see Data Table 1) that shows the possible outcomes from a cross between a heterozygous male and a heterozygous female.

7. Write a hypothesis, using the Punnett square to determine the approximate number of seedlings (and percentages) that will have a dominant trait and that will have a recessive trait out of the 50 seeds.

8. Once the majority of seeds have germinated, remove the lid of the Petri dish and count the number of seedlings that are green versus those that are yellow.

9. Record the data in Data Table 2.

Questions:

A. What are the predicted ratios of the phenotypes in the plants?

-The predicted ratios of the phenotypes in the