Lesson Plan
Date: July 16, 2010
Patrice Hopkins
Subject: DNA EXTRACTION FROM WHEAT GERM
Objectives:
1. After the lesson students should be able to understand a process of DNA
extraction.
2. After the lesson students should be able to observe some of the physical
and chemical properties of DNA.
3. After the lesson students should be able to use scientific process skills to
sketch and label the process of DNA extraction.
Motivation: The teacher will begin the discussion of where wheat originated. The teacher
will tell students that nearly one-third of all land in the world used for crop production is
planted in wheat. Wheat probably originated in the Middle East and was an important food for
the ancient Mesopotamian, Egyptian, and Indus civilizations. Wheat germ comes from the seed
of the wheat plant. Today we begin the process of extracting DNA from wheat germ.
Introduction:
This lab is a great review of cell structure and biochemistry. A complete
copy of DNA is found in every cell in any organism. In order to release the DNA to analyze it,
you must break open the cells and remove structural proteins that interfere with the DNA
structure. The procedure following below is a simplified procedure to release a good amount of
DNA so that the student can see it. It allows observation of DNA’s physical and chemical
properties.
Prior Learning:
Each student must have background knowledge of the concepts below before completing this
lab. activity.
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DNA is found in the cell of every living organism.
Proteins and enzymes may obscure seeing the DNA, so it must be removed.
You must break through a cell membrane or cell wall to release DNA.
Among eukaryotes DNA is contained in the membrane wrapped nucleus.
DNA in prokaryotes is floating free in the cytoplasm.
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Typing to Prior Knowledge:
The teacher will have students to review the process of
DNA extraction from wheat germ. The teacher will allow students to infer how they would
distinguish between the independent, dependent, and controlled variables in this experiment.
Instructional Strategy: WORDSPLASH
The teacher will have students to recall key terms from previous terms or concepts selected
from readings regarding DNA. These terms should include cell structures, genetic code,
nitrogen bases found in DNA, base pairing, purines, pyrimidines, chromosomes, RNA, DNA, cell
wall, cell membrane, nucleus, etc. Students should be familiar with the vocabulary. The
newness or novelty in this context is the way in which the terms are associated with the new
topic about to be studied. The selected terms are displayed randomly and at angles on a visual.
Students are asked to brainstorm and generate complete statements (not just words or
phrases) which predict the relationship between each term and the broader topic. Once
statements are generated, students turn to the printed materials, read to check the accuracy of
their predictive statements, and revise where needed. Students will create the WORDSPLASH
prior to viewing the virtual lab. Biotechniques Virtual Lab. How to Extract DNA from Anything
Living. http://learn.geneticsutah.edu/content/labs/extraction/ . And as a summarizing strategy,
students read and then create their own WORDSPLASH of what they consider to be the key
terms or ideas in the passage.
Development/TEACH continued:
Experimental Variables – Setting the Stage
The Problem: You are working at a company that makes DNA for sale to other scientists and
research institutions. Since your company want to stay in business, the DNA it sells must be of
good quality and each extraction must give the highest possible yields. The basic procedure has
been established for extracting DNA from wheat germ. Students will be asked to analyze the
materials, procedure, run the experiment, and distinguish between what they believe would be
the independent, dependent, and controlled variables.
The Brainstorming Session: The lab supervisor (teacher) calls a meeting of all the
biotechnicians (students) to brainstorm ways to improve yield by modifying the procedure.
Students will also be asked to identify and list variables.
1. Students are to write down their suggestions for changing the procedure such as
changing the amounts of brands of wheat germ, meat tenderizer, dishwashing liquid,
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water, type and temperature of water, and percent and temperature of ethanol (alcohol).
Other considerations may be stir mechanics (i.e. vigorous versus easy stirring or shaking
versus swirling).
2. Each group of students chooses a parameter (or two) to explore and design experiments
to test the parameter changes. Students will hand these parameter changes into the
teacher for approval.
The Research and Modification: The groups perform their experiments and write up their
results and conclusions. These are presented to the entire company (class) about whether
their modification should be included in the company S.O.P. (Standard Operating
Procedures).
Note: The teacher will review the following:
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Explain that in all experiments, an investigator changes the independent variable
and observes the effect of that change on the dependent variable.
Emphasize that each experiment must have only one independent variable.
Emphasize that a controlled variable is held constant during an experiment.
ACTIVITY
Materials:
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250 ml flask
1 gram of wheat germ (raw)
3 X 5 ml pipettes
1 gram of meat tenderizer (no MSG)
1 M sodium bicarbonate
Dawn dishwashing liquid
Isopropyl Alcohol
Thermometer
Timer
Paper towels
Ice bucket
5 & 10 ml graduated cylinders
1 ml pipette
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Note: The raw wheat germ, meat tenderizer (NO MSG), sodium bicarbonate, Dawn
dishwashing liquid, Isopropyl Alcohol, etc. can be found at Meijer or Super Kmart &
Zerbos Health Food Store.
Procedure:
1. Measure 22.5 ml of tap water into a 100 ml flash.
2. Place the flask in a 55 C water bath fir 5 minutes.
3. Sprinkle 1 gram wheat germ from the plastic bag into the flask with water and gently
swirl.
4. Place 1.5 ml of Dawn dishwashing liquid into the flask with a pipette and gently
swirl.
5. Place the flask in 55 C water bath for 5 minutes.
6. Gently stir 1 gram of meat tenderizer (without MSG) from the plastic bag.
7. Add in 2.5 ml of 1 M sodium bicarbonate with a pipette and stir the solution.
8. Place the flask back in the water bath for 15 minutes. Longer incubation times will
cause excessive breakage of the DNA strands.
9. Transfer the flask containing the wheat germ mixture to an ice bucket for 5 minutes.
Swirl gently while mixture is cooling.
10. Slowly layer 5 ml of ice-cold isopropyl alcohol over the wheat germ solution in the
flask using a 10 ml pipette. Allow the alcohol to flow out of the pipette at the side of
the flask. The flask can be removed from the ice for this step.
11. There will be a visible interface between the alcohol layer and the wheat germ
solution layer. The solubilized DNA contacts the alcohol where the two liquid layers
meet. You should see a white fibrous substance at the interface. This is DNA.
Assessments: Oral/Written/Video segments
PRE-LAB Activity (Students are to complete after reading the introduction, material,
and procedures).
Directions: students must read questions carefully and answer questions in
complete sentences.
1. Where is DNA located? (Specifically)
2. What does the Dawn liquid and swirling of flask do to the DNA solution?
3. How often should the solution be mixed once the Dawn is added?
4. What must be done with the alcohol?
5. Where should you first be able to see DNA in the solution?
6. What can be used to remove the DNA from the solution?
7. How can the DNA be saved?
8. What does sodium bicarbonate do to the solution?
Page 5 Assessment continued:
DNA EXTRACTION LAB REPORT
Name _____________________ Date_______________ Class Period___
Note: use your lab notebooks to write questions and answers.
Question: How can DNA be extracted from wheat germ? Describe extracted DNA.
Write experimental data for this experiment.
Analyze data/conclusion
Research References:
Lab Hypothesis:
Homework questions:
1. Make a drawing of your extracted DNA.
2. What solution was used as an enzyme in this experiment? And what does the
enzyme used in this experiment do to the DNA?
3. What lyses the cell and nucleus?
4. What protects the DNA?
5. When does precipitation of DNA occur?
6. List some controlled variables in this experiment.
7. What is the dependent variable?
Closure: As a summarizing strategy, students will read their notes from
brainstorming, class discussions, and lab report and then create their own
WORDSPLASH of what they consider to be the key terms or ideas in the lesson
on wheat germ extraction.