Cotton and Cabbage

Nadja Wehmeyer1, Kirstin Bittel2 , and Rachel Hughes3

  1. BioTECH Project, MCB Dept., University of Arizona
  2. MansfeldMiddle School, Tucson, AZ.
  3. Southwest Environmental HealthSciencesCenter, University of Arizona

Abstract

Students have been introduced in “Just what are you Eating?” to genetically modified food (GMF) and the controversy surrounding GMF. During this exercise students are introduced to a specific genetically modified organism. Students plant a variety of cotton seeds including Bt cotton and then using the cabbage looper moth and RoundUp herbicide determine which plant is genetically modified and what it is modified with. Throughout the exercise students are able to observe both the lifecycle of the moth and the cotton. The exercise covers several weeks. Day 1 of the exercise includes planting of the cotton, and design of their experiment. Also on day 1, students identify possible uses for GMO. Subsequent days during the cotton’s germination and growth require only a small amount of time for maintenance purposes. At approximately 3 weeks students will assess the effectiveness of Bt cotton, and which plants are Bt Cotton. This exercise will vary in length and depth dependent on the individual teacher and the class. It is advisable that teachers plant some seeds in advance. This activity is based in part on the products on BioTECH’s Biology Bootcamp, specifically the work of Andrew Lettes and Mike Smith.

Standards

Content Area C - Life Science

The Cell

Cells store and use information to guide their functions. The genetic information stored in DNA is used to direct the synthesis of the thousands of proteins that each cell requires.

The Molecular Basis of Heredity

In all organisms, the instructions for specifying the characteristics of the organism are carried in DNA, a large polymer formed from subunits of four kinds (A, G, C, and T). The chemical and structural properties of DNA explain how the genetic information which underlies heredity is both encoded in genes (as a string of molecular "letters") and replicated (by a templating mechanism). Each DNA molecule in a cell forms a single chromosome.

Content Area A - Science as Inquiry

Objectives

Students will be able to:-

Day 1

  1. identify 4 uses of GMO: as possible vaccines, as pesticides, as herbicides and as way to produce food colorations.
  2. recognize that the use of the letters Bt before a crop means that crop has had a gene inserted into its genetic makeup that originates from the Bacillus thuringiensis bacterium. This gene produces a protein toxic to many insects.
  3. identify a number of manners of seed dispersal

Day 14 onward

  1. describe the lifecycle of the cotton plant and cabbage looper moth.
  2. determine the effectiveness of a genetically modified plant against a pest insect
  3. collect and analyze data
  4. design an inquiry using their understanding of Bt cotton and the cabbage looper

Teacher Background

Link to GMO

Noctuid moths and cotton biology (not letting cotton go to seed)

Bacterium thuringiensis

Regulation of plants and insects

- describes a PCR activity using Bt-cotton

- was an inspiration for this exercise, you can find more great exercises at:

- shows a class sample of cotton plants before and after the attack of the cabbage looper!

Related Websites

Time: Approx 2 days and small portions of several days

Preparation Time: Gathering pots, plastic cups, netting, soil, seeds, ordering insects, materials for inquiry

Materials:

Bt cotton and regular cotton seeds (we found ours at…)

Soil

Pots (specific type to order from SOLO cup.)

See through plastic cups, 4 and 16oz

Netting

Cabbage loopers (obtained from USDA) (not needed till week 3)

RoundUp (not needed till week 3)

Planting diagram

Experimental design sheet

Important Considerations!

  1. Do not let the Bt cotton go to seed. Typically it is difficult to get it to this point.
  2. Do NOT release cabbage loopers as caterpillars or moths, dispose of them by freezing them

If you can’t get Bt cotton or cabbage loopers: this exercise might be performed using Manducasexta available from and Bt tomato or Bt tobacco. Manducas do have a different life cycle and you will have to adjust planning accordingly. More information can be found at

Activity

Day 1

1. During the last class period students were asked to review their evening meal to see what the prevalence of GMF’s are on their diet. Engage students by connecting to yesterday’s class and homework. Ask them if they had GMF in their dinner?

“Yesterday we discussed the prevalence of GMF in our diet, what did you notice in your dinner last night? Any GMF’s?” Discuss what might have been in their dinner and ask why those particular plants might have been modified. Set up a chart with possible modifications of genes.

2. Introduce the seeds to the students, “I actually have some genetically modified organism seeds here along with some wild type seeds. They are color coded so I can tell the difference. I am, however, not going to tell you the difference! I’m also not going to tell you what they have been modified for, but I am going to expect you to determine which is the genetically modified plant and provide evidence in support of that.”

3.Tell the students that you will narrow the types of possible modifications to three. 1) The plant contains a gene that makes it not susceptible to the herbicide RoundUp. 2) The plant contains a gene which is taken from the Bacillus thuringiensis bacterium. This bacterium is a natural insecticide. 3) The plant contains a gene which quickens the plant’s lifecycle. Providing students with information sheets about these three different types of modification may be useful.

4. Provide students with information about how to plant the seeds. As a hint tell them that they should design their planting pots using the solo cups with the netting across; see the planting diagram.

  1. In their groups students should identify the variables involved and controls needed in testing these plants for specific genetic modifications. Students should write out their experimental design, figuring out how many seeds and pots they will need. Before receiving soil, seeds and plants students should get approval on their design. See design sheet.
  1. Students plant seeds. Remind students that they are responsible for taking care of the plants and watering them. Students should make daily observations over the next three weeks until the next stage of the lab.

Day 20 from seed planting

  1. Introduce the tools to test the plants with, RoundUp and Cabbage looper egg masses. Students may already have come to a decision about the third option- a more robust plant- as they should be measuring the plants daily.
  2. Prior to today students have been looking at some of the issues associated with the use of pesticides and herbicides. This is a good time to remind them about what they have learned while handling the RoundUp. Spraying the plants should occur in a well ventilated area.
  3. Students apply treatment and watch for the next few days. What happens?

Day 24 from seed planting

Students use the information sheets to support their explanations as they write up their lab report.

Assessment

Students’ explanations of their results may be evaluated.