Strawberry Smoothies
Adapted from:
BIOLOGY science for life
Laboratory manual
Instructors edition, second edition
AND
Drugs, DNA, and Detectives
A high school curriculum for Chemsitry and
Biology
Strawberry DNA Lab
By Meredith Penland CCU GK-12 Fellow
This lab allows students to see DNA, understand where it is located in the cell and how it can be
extracted. This lab can be done in a 90 minute class period and is easy to set up and easy to
clean up.
State Standards
This lab activity supplements standard indicators B 4.1- B4.3 concerning DNA structure and
function.
B- 4. The student will demonstrate an understanding of the molecular basis of heredity.
Objectives
1.
2.
3.
4.
Students will learn the double helix structure of DNA.
Students will understand what makes up a phosphate group.
Students will review the structure of the nuclear and cellular membrane.
Students will be able to see DNA.
Lesson Plan
Question: Does every organism have DNA?
Introduction
1. Review what DNA is and what does.
2. Review where is it located within the organism and within the cell.
3. Does DNA have the same structure in all cells?
4. Review double helix structure of DNA.
Important information
1. Hand out lab sheet and go over the necessary steps for DNA extraction.
2. Elaborate on how it is possible to extract DNA from a cell. Discuss how the soap in the
buffer solution breaks down the cell wall and allows the DNA to be extracted.
3. Refer back to the students’ knowledge of polar attractions between molecules. Explain
why the salt was added to the buffer due to the polarity of the phosphate group and the
salt.
4. Explain why ice cold ethanol must be used to completely extract the DNA from the
strawberry cells.
5. Go over vocabulary
a. Filtrate
b. Interface
c. percipitate
Experiment
1. Create DNA extraction buffer before class.
a. Buffer can be mixed by either of the following methods
i. 100 mL shampoo no conditioner, 15 g NaCL, and 900 mL water
ii. 50 mL liquid dishwashing detergent, 15g NaCl and 950 mL water
2. Students should work in no more than groups of two. This is not a hard or complicated
lab. But students really enjoy it.
3. Students follow steps on the lab hand out provided.
Assessment
Lab protocol and worksheet are provided. Worksheet includes questions about lab
results, DNA structure, and the use or reagents in the buffer.
Teacher information
A ppt is provided to explain details of the lab and use of reagents modified from UC Davis
Materials needed for each pair of students
1. 1 Zip-lock baggie
2. 1 strawberry (fresh
or frozen and
thawed)
3.
4.
5.
6.
Cheese cloth
Funnel
100 mL beaker
Test tube
7. Pipette or glass stir
rod
8. Rubber band
Name_____________________________ Block ____________________Date_______________
Strawberry Smoothies
Introduction
DNA (Deoxyribonucleic acid) is found in the cells from Animals and Plants. DNA is a double stranded
macromolecule composed of nucleotide bases pairing Adenine with Thymine and Guanine with
Cytosine. DNA can be extracted from cells by a simple technique with household chemicals, enabling
you to see strands of DNA with the naked eye.
Safety Precautions
Wear safety goggles
Do not eat your strawberry smoothie, denatured ethanol is poisonous.
Materials (per student group):
1.
2.
3.
4.
5.
6.
7.
8.
1 Zip-lock baggie
1 strawberry (fresh or frozen and thawed)
Cheese cloth
Funnel
100 mL beaker
Test tube
Pipette or glass stir rod
Rubber band
Procedure:
1. Place one strawberry in a zip-lock baggie
2. Smash strawberry with fist for two minutes.
3. Add 10 ml of extraction buffer to the bag
4. Mush again for one minute
5. Attach cheese cloth to beaker with rubber band
6. Filter strawberry mush through cheese cloth into beaker
7. Dispose of excess strawberry mush and cheese cloth
8. Pour filtrate though funnel into test tube
9. SLOWLY pour ice-cold ethanol into test tube until the tube is ½ full
10. At the interface, you will see the DNA precipitate out of solution and float to the top.
Spool the DNA on your pipette or glass rod.
Describe and draw a picture of your final product in the space below
Once you have extracted DNA from your strawberry please answer the
following questions
1. Where is DNA found in the cell?
2. Discuss the action of the soap on the cell. What was the purpose of the soap in the
buffer?
3. Why was the Sodium Chloride included in the buffer? Please discuss how the polarity of
the particles affected the phosphate group.
4. Why was cold ethanol added to the strawberry buffer mixture?
5. On the back of this lab sheet draw a diagram of DNA containing 5 sets of nucleotide
bases labeling the hydrogen bonds between the bases.