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Cotton
and Cabbage
Nadja
Wehmeyer(1), Kirstin Bittel(2), and Rachel Hughes(3)
1. BioTECH
Project, MCB Dept., University of Arizona
2. Mansfeld Middle School, Tucson, AZ.
3. Southwest Environmental Health Sciences Center,
University of Arizona
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| Time: |
Approximately
2 days and small portions of several days thereafter. |
| Preparation
Time: |
Gathering
pots, plastic cups, netting, soil, seeds, ordering insects,
and materials for inquiry. |
| Materials: |
B\Bt-cotton
and regular cotton seeds
Soil
Pots (specific type to order from SOLO cup…)
See-through plastic cups, 4 and 16oz
Netting
Cabbage Looper Moths (obtained from the USDA- not needed until
week 3)
RoundUp (not needed until 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 Looper Moths as caterpillars or moths,
dispose of them by freezing them
Abstract
Students
have been introduced in “Just what are you Eating?” to
genetically engineered food (GEF) and the controversy
surrounding GEF. During this exercise students are
introduced to a specific genetically engineered organism.
Students will plant a variety of cotton seeds including
Bt cotton and will then create experiments using the
Cabbage Looper Moth and RoundUp herbicide to determine
which plant is genetically engineered and what trait
has been added. Throughout the exercise students are
asked to observe both the lifecycle of the moth and
the cotton. The exercise covers several weeks. Days
1-2 of the exercise includes planting the cotton and
designing the experiment. Also on days 1-2, students
identify possible uses for GEO. 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 which plants
are Bt Cotton and how effective the engineering of
this plant is. This exercise will vary in length and
depth depending 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.
Objectives
Students will be able to:
Days 1-2
1. Note how given traits could be achieved by selective
breeding and by transgenesis.
2. Identify different uses of GEO (to create
possible vaccines, to express relevant pesticides
or herbicides
and as way to produce food colorations).
3. Recognize that the use of letters (Bt) before
an organism’s name means that the organism has had
a gene inserted into its genetic makeup that originates
from another organism (the Bacillus thuringiensis bacterium).
This gene produces a protein toxic to many insects,
and previously extracts of the bacteria had been applied
to achieve the same goal.
4. identify multiple ways that seeds can disperse
Day 14 and onward:
1. Describe the lifecycle of the cotton plant and
Cabbage Looper Moth using pictures and words.
2. Determine the effectiveness of a genetically
engineered plant against a pest insect and an
herbicide; describe
the specificity of the change.
3. Collect and analyze data
4. Design an inquiry using their understanding
of Bt cotton and the Cabbage Looper Moth.
National Science Education 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 Teacher Background
As has been covered in the previous lesson in the
teacher background, genetic modifications of
agriculturally important organisms have been
conducted since the advent of agricultural practices.
In this lesson, students get to have hands-on
experience with a genetically engineered organism,
Bt-cotton.
Bt (Bacillus thuringensis) is a soil bacterium. B.
thuringensis makes a toxin that, when ingested by
insects, affects the digestive tract to decrease
their ability to obtain nutrients from their food.
Insects die either by starvation or by septicemia.
Until recently, extracts or slurries of this bacteria
were prepared to spray on crops (called a foliar
treatment). These had a limited time period in which
they were active, as they had to be in the right
place and time to be munched on by the insects and
they do degrade in the environment.
Scientists more recently (mid 1980’s) found
a way to incorporate the gene for the toxin into
the genome of the plants affected by these insects.
This way, the plant makes the toxin and insects that
feed on the plant leaves (where the toxin is expressed)
will ingest it and have the same effect as if they
had ingested the bacteria. Incorporating the gene
is done using either a vector (a plasmid of Agrobacterrium
tumefaciens that scientists put the desired gene
into and will incorporate it into the genome of the
plant.) or by shooting tiny metal balls covered with
the desired gene into plant cells which will then
incorporate these segments into the genome.
For more information, use the sites below.
Related Websites
Link to GEO related information
http://pewagbiotech.org/resources/factsheets/display.php3?FactsheetID=2 -
2003 state of genetically engineered crops in the US,
emphasis
on soy, cotton and corn.
http://www.sciencedaily.com/releases/2000/09/000904092612.htm - describes the impact of genetically engineered herbicide
tolerant crops on bird populations
http://www.biotechknowledge.monsanto.com/biotech/bbasics.nsf/faq.html - OpenPage
- Monsanto site that gives genetic engineering information
Cabbage Looper Moths and cotton biology
http://creatures.ifas.ufl.edu/veg/leaf/cabbage_looper.htm – cabbage
looper biology and lifecycle
http://www.mhhe.com/biosci/pae/botany/botany_map/articles/article_30.html - info on cotton biology
Bacillus thuringiensis - it should be clear
that Bt and transgenic use of Bt toxins are different
things
http://www.ext.colostate.edu/pubs/insect/05556.html -
overview of Bt- very reader friendly.
http://ace.orst.edu/info/npic/factsheets/BTgen.pdf -
overview of Bt, more scientific w/ LD50 values and references
http://www.umass.edu/umext/ipm/ipm_projects/landscape/bt.pdf - short synopsis of Bt for foliar application
GEO’s in the classroom
http://biotech.biology.arizona.edu/labs/bt_cottonSG.html - describes a PCR activity using Bt-cotton, begins with
an ok commentary on the differences between selective
breeding (artificial selection) and transgenesis
http://www.uga.edu/discover/educators/activities/act6.pdf -
was an inspiration for this exercise, you can find more
great exercises at: http://www.uga.edu/discover/educators -
compares Bt and non-Bt corn with European Corn Borers
(ECB’s)
http://www.angelfire.com/az3/a_lettes/2002/btcotton/plant.html - shows a class sample of cotton plants before and after
the attack of the Cabbage Looper Moth!
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Activity
Initial question on the board: “How
does genetic engineering of organisms differ from modifying
their genes with selective breeding?”
Day 1
1. During the last class period students were asked to
review their evening meal to see what the prevalence of
GEO’s are on their diet. Engage students by connecting
to yesterday’s class and homework. Ask them: “Yesterday
we discussed the prevalence of GEO in our diet, what did
you notice in your dinner last night? Any GEO’s?” Discuss
what might have been in their dinner and ask why those
particular plants might have been engineered. Set up a
chart with changes that might be desirable.
(If students seem interested in how this is done, you might
use the following to demonstrate transgenesis: http://www.pbs.org/wgbh/harvest/engineer/,
they will get a chance to do this again later in the semester
in “Chocolate Flavored Cherries”)
2. Introduce the seeds to the students, “I actually
have some GEO 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 changes have been made,
but I am going to expect you to determine which is the
genetically engineered plant and provide evidence in support
of that.”
3. Tell the students that you will narrow the types of
possible changes to three. 1) The plant contains a gene
that makes it not susceptible to the herbicide RoundUp.
2) The plant contains a gene that is a natural insecticide.
3) The plant contains a gene that accelerates the plant’s
lifecycle.
4. On the board, list each of the changes and have students
describe how each might be accomplished by selective breeding.
Then remind them that, in this case, the traits have been
added through genetic engineering. On the board take down
their ideas about where these traits could have been taken
from (1-tough weeds, perhaps, 2-something that kills insects,
either another plant, bacteria, virus, 3- a fast growing
plant). Ask students if it is possible to selectively breed
anything (green polka-dot corn, for example)? Is it possible
to genetically engineer anything?
5. 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; consult the planting diagram.
6. In their groups students should identify the variables
involved and controls needed in testing these plants for
specific engineered genes. 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.
7. Students plant seeds. Remind students that they are
responsible for taking care of the plants and watering
them. Students should make DAILY observations and measurements
over the next three weeks until the next stage of the lab.
Day 20 after seed planting
8. Introduce the tools to test the plants with- RoundUp
and Cabbage Looper Moth 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.
9. 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 be done in a well-ventilated area.10. Students apply
treatment and observe for the next few days. What happens?
They should record what happens in their science notebooks.
Day 24 from seed planting
11. Students use the information sheets to support their
explanations as they write their lab report.
Closure
This is a long project, so make
sure to make time to talk with students about how this experiment
fits in with the
rest of the lessons in this unit. They are using an organism
that has been changed through our knowledge of how genetics
works and the improving of technology to allow us to manipulate
genes. Ask them to consider what this means to them. Throughout
the semester they are increasing their knowledge, and ultimately
realizing different ramifications to these technological
advances. Be sure to bring this all up again in “Golden
Rice or Frankenfood”.
Homework
Students will be asked to complete a lab report at
the end, using information sheets/data sheets they have
kept over the previous 3.5 weeks. Some of the questions
asked in class on the first two days could also be take-home
questions to answer as a family. Students’ explanations
of their results may be evaluated.
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Embedded
Assessment
There are opportunities
for group participation throughout this lesson. Evaluate group
dynamics, follow-through and organization. Also, as this lesson
spans a long period of time, there is ample opportunity to
have students reflect on their evolving ideas about transgenic
crops. |
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