Name:____________________________________________
Date___________________________
Class Period:__________
Laboratory Activity: Extracting DNA from Strawberries
Do Now: Pre- Lab Questions
Answer the following questions using complete sentences:
1. Where in the cell is DNA found?
2. What are DNA molecules called? Hint: humans have 23 pairs of them.
3. What do you think the DNA will look like when we extract it from the
strawberries?
Learning Objectives:
By the end of this class, you will be able to:
1. Make predictions about the appearance of DNA
2. Discover and explain how we are able to remove DNA from cells and see it
even though DNA is very small and can usually only be seen with a powerful
microscope
3. Predict traits that could be given to strawberries using biotechnology
4. Determine how the leafy green part of strawberries appears so different
from the red fleshy part of the strawberry
PowerPoint Presentation:
Pay attention to the presentation and fill in the missing information below.
1. Vocabulary Review:
Word
1.
2.
3.(noun)
Definition
3.(verb)
4.(noun)
4. (verb)
5. (noun)
5. (verb)
6.
7
8.
9.
10.
11.
2. Background Information:
The long strands of DNA store the genetic information of living things. DNA is
present in every cell of plants, animals, and other living things, with one exception.
What cells have no nucleus and therefore have no DNA?
The DNA found in strawberry cells can be extracted using common materials. We
will use a DNA extraction buffer. This extraction buffer will help us remove the DNA
from the strawberry cells. It contains _______________________ and ____________________.
The _____________________ breaks up the ____________________ proteins that the DNA is
wrapped around.
The ______________________________ dissolves the phospholipid part of the strawberry
_____________________ and ____________________________ membranes.
3. Laboratory Safety
None of the chemicals or materials we will be using in this lab are particularly
dangerous. However, you must be careful and follow a few basic rules:
1. DO NOT EAT ANYTHING. I know the strawberries look delicious. Do not
eat them. Today, they are not food, they are laboratory materials.
2. BE CAREFUL WITH THE SCISSORS. Mrs. Campbell will demonstrate the
correct way to hand somebody a pair of scissors.
3. WASH YOUR HANDS after you have finished the lab activity.
4. POUR LIQUIDS CAREFULLY. Do not splash any liquids on purpose. If you
spill something, wipe it up with a wet paper towel, then wipe the surface
again with a dry paper towel.
Breaking the rules will cause you to lose your lab privileges. You will have to sit in a
chair in the back of the room and watch everybody else do the lab. Continued
disruptive behavior will earn you a referral.
Laboratory Materials
Check your table to make sure you have the following items:
Plastic zip-top bag
1 strawberry
DNA extraction buffer
Cheesecloth
funnel
ice cold isopropyl alcohol
scissors
wooden skewer
test tube rack
test tube
Laboratory Procedure:
1. Assemble your filtration equipment as shown in the picture on the previous page.
2. Place one strawberry in a zip-top bag. Squeeze out the excess air and seal the bag
tightly.
3. Gently squish, knead, and grind the strawberry with your fist and fingers for two
minutes. Be careful not to break the bag!
4. Add 10mL of DNA extraction buffer to your bag. Squeeze any excess air out of the
bag and seal tightly.
5. Gently squish the buffer together with your smashed strawberry for one minute.
Try not to create too many bubbles.
6. Cut the tip off the corner of the zip-top bag and gently pour your strawberry
solution on top of the cheesecloth.
7. Let the solution drip through the cheesecloth, down the funnel, and into the test
tube. DO NOT force the strawberry solution down into the funnel.
While you are waiting for your solution to filter, answer question 1 in the
Conclusions and Analysis section on the next page of this handout.
8. Slowly pour 20mL of cold isopropyl alcohol down the side of the tube. Allow this
to sit for one minute.
9. Dip the skewer into the tube where the strawberry extract layer meets the
isopropyl alcohol layer. Gently swirl the skewer around where the layers meet and
slowly pull the skewer up the side of the tube.
10. Observe your DNA!
Conclusions and Analysis
1. Write the letter of the procedure step next to its function.
A.
B.
C.
D.
Procedure Step
Filter strawberry solution through
cheesecloth
Squish and knead strawberry with
DNA extraction buffer
Squish and knead strawberry in the
bag by itself
Add cold isopropyl alcohol to test
tube
Function
To precipitate DNA
from solution
To separate the
components of the
cell
To break open the
strawberry cells
To break up
histone proteins
and dissolve the
cell and nuclear
membranes
Answer the following questions using complete sentences.
2. What did the DNA look like? Relate what you know about the structure of DNA to
what you observed today.
3. Explain what happened to the DNA during the step when you added isopropyl
alcohol to your strawberry extract (hint: DNA is soluble in water, but not in isopropyl
alcohol).
4. A person cannot see a single cotton thread from 50 feet away, but if you
combined thousands of threads together into a thick rope, you would be able to see
it from 50 feet away. Is this statement analogous to our DNA extraction? Explain
your answer.
5. Why is it important for scientists to be able to remove DNA from an organism?
Give two reasons.
6. Is there DNA in the food you eat? How do you know?
7a. What do you think are some desirable traits in strawberries? (Hint: think about
what farmers might want in a strawberry and what customers might want in a
strawberry)
7b. How could biotechnology be used to put these desirable traits into
strawberries?
8a. Could we have extracted the same DNA from the green leafy part of the
strawberry? Explain your answer.
8b. Why do you think we used the red fleshy part of the strawberry instead of the
leafy green part?