Mendel's law of Independent Assortment

Lesson Plan

State Standards:

Essential Question:

Lesson Questions:


How can we make genetics come to life? Do you have a green thumb? We have currently been studying Mendel's laws of inheritance and how these laws can be applied to many organisms. This lesson will use Wisconsin fast plants to demonstrate Mendel's law of dominance, the law of segregation, and the law of independent assortment to the world around us.
This activity will engage you in a hands-on experiment to see evidence of these principles.

Brassica rapa is a rapid-cycling brassicas. They are members of the crucifer family of plants, closely related to cabbage, turnips, broccoli, and other cruciferous vegetables. They have been bred over 30 years at the University of Wisconsin. We will use them in this experiment because they have an average life cycle of approximately 35 days. Brassica rapa is an ideal organism for studying genetics because of this short life cycle, is relatively inexpensive, easy to keep large numbers, and one does not need a "green thumb" to work with these organisms.


You and a partner will design and conduct an experiment using Wisconsin Fast Plants to model Mendel's laws of inheritance. In addition, data will be recorded, analyzed, and presented to the group. A final laboratory report will be produced at the end of the experiment.

  1. You and your partner will need to examine each of the different types of Wisconsin Fast Plants. You will need to record the phenotypic information and genotypic information regarding the different populations of plants.
  2. You and your partner will design an experiment to test the predicted offspring with the actual offspring of a particular cross. I will assign you and your partner to one of the following groups:
    1. Group 1: Design a procedure to produce a population in which 75% of the offspring is composed of purple stems and 25 % of the
      offspring is composed of green stems.
    2. Group 2: Design a procedure to produce a population in which 50% of the offspring are composed of purple stems and 50% of the
      offspring are green stemmed.
    3. Group 3: Design an experiment in which the offspring show a 9:3:3:1 ratio of purple-stemmed, tall, purple-stemmed short, green-stemmed tall, and green-stemmed short.
  3. You and your partner will present your ideas on how to obtain the offspring you were assigned using a poster paper diagram of what you plan to do.
  4. You and your partner will create a diagram of the plants and a Punnett square of each of the crosses necessary to obtain the offspring assigned to your lab group.
  5. After any changes to your procedure, you and your partner will conduct your experiment and collect data. Throughout the activity, the following exercises should be completed. You will find information for each under the resources section.
    1. Watch the Pollination of Wisconsin Fast Plants
    2. Read about the plant reproductive life cycle and Mendel's laws of inheritance from your textbook.
    3. Experiment with Google documents
    4. Read and reflect on a passage from Mendel's journals
  6. Over the course of the next month, you and your partner will record data, graph and analyze data, and make conclusions about your data.
  7. At the end of the experiment, you and your partner will write a report and present findings to the class.

Lesson Experiences:

After this experiment, you will have:

    • Formulated a hypothesis.
    • Designed an experiment.
    • Collected and recorded data.
    • Worked collaboratively with others in your class.
    • Presented experiment and communicated findings with the class.
    • Used a digital camera to film growth phases of your specimens.
    • Cross-pollinated plants.
    • Learned the reproductive cycle of plants.
    • Compared predicted results to actual results of genetic crosses.
    • Used Google documents to record information and write a lab report.
    • Witnessed Mendel's laws of inheritance first hand!


Over the course of a month and half, you and your partner have worked with Brassica rapa and have witnessed two life cycles of this organism. The results of these life cycles can be analyzed and compared to the predicted results that you and your partner created at the beginning of the activity. After review of the data, it will be easy to witness Mendelian laws of inheritance. In addition, you have had experience with science research.


After completing this experiment, you will have been assessed in the following ways:


Image Credit: Fast Plant Life Cycle