DNA Extraction Lab
Why is DNA Extraction Important?
DNA is the code for all known life on this planet. Using the
information stored in DNA organisms are able to build, repair and
reproduce themselves. This information will determine all an
organisms traits; height, color, gender, species, and everything else you can think of.
DNA can be removed from organisms through a common and
useful scientific procedure called DNA Extraction. DNA extraction is a
vital procedure in the field of genetics or any field that relies on DNA
such as medicine. By extracting DNA from an organism scientists are able
to study its structure and the genes found inside that code. Below is a
small list of things you may use or know about that need DNA extraction;
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Extracted DNA is used to develop treatments for many
diseases in humans. By looking at our genes and how the
disease works we can develop Gene Therapies to help
manage a genetic disorder.
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Extracted DNA is used to solve crimes by creating a “genetic
fingerprint” for each individual and this same technique is
how paternity and maternity tests are done.
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Extracted DNA can be studied to find the best possible genes.
Then, scientists can use these genes to develop strong,
disease-resistant crops that require little to no pesticides.
The above list contains just a few of the things that depend on
DNA extraction. And now, you are going to extract the DNA from
strawberries first, and then from other fruits to compare them.
Opening Questions:
1. What is DNA? What is the function of DNA inside organisms
2. The process of removing DNA from cells is called ________________________________.
Describe two things extracted DNA is used for in our society.
Materials:
Collect the following materials before proceeding.
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1 reseal able plastic bag
1 coffee filter
1 plastic cup
_____ strawberries
1 coffee stirrer
Procedure:
Working together in groups of ________ read through each part before you start and follow the
steps in Parts I, II, III and IV.
Part I – Preparing the strawberry
1.
2.
3.
4.
Remove all the stems and “green” from the strawberry and place this in the trash.
Place the strawberries in your plastic bag and seal it.
Mash your strawberries (gently) with your hands for 2 minutes.
Add a spoonful of DNA Extraction Buffer to your plastic bag. (Buffer will be located at
the front of the room)
5. Mash again for 1 minute.
6. Important: Let the strawberry soak in the DNA Extraction Buffer for 6-8 minutes before
moving on! While you wait, answer the following questions.
1a. What do you think was the purpose of mashing the strawberry?
2a. Where is DNA located? _____________________________________
3a. Turn the following DNA Strand into a protein;
TAC – AGT – TTG – GCG – AAC – AAG – GTG – ATC
mRNA strand –
Polypeptide Part II – Straining the strawberry
1. Put the coffee filter into the cup and pour the contents of your plastic bag on top.
2. Let the mixture sit for a few minutes to drain through.
3. After a few minutes, you can gently squeeze the mixture to finish draining, but do not
squeeze too tightly.
4. Throw away your strawberries!! Do not put the filter on the desk!!
Part III – Seeing the DNA!!
1. Once you have your mixture in the cup, it’s time for the final steps.
2. Take your cup to the front of the room. Turn the cup slightly on its side and gently pour
about the same amount of rubbing alcohol as you have strawberry mixture.
3. DO NOT MIX TOGETHER!!
4. Congratulations! You’ve just isolated DNA. Take the cup back to your seat and watch
until you see a white cloudy substance. That would be the DNA.
5. Tilt the cup again and use the coffee stirrer to wrap the DNA into a bundle and pull it
out to look at it. Then, put your DNA back and leave it there.
Part IV – Let’s Mash other Stuff!
1. Now, grab some other foods (banana, raspberry, kiwi) and repeat Parts I – III for the new
food. IMPORTANT! – If you use the banana or kiwi do not use the entire fruit. Cut them
over a sink and only use part.
2. You must do at least two other foods. Once you complete your other foods continue to
the next steps.
3. Clean up your work area. Keep only the three cups of DNA, throw everything else away.
4. From the front of the classroom take as many petri dishes as you have cups (at least 3).
5. Mass the petri dishes and record them in the table. Then add your DNA to each and
record the difference in mass.
6. Once you have all of your mass measurements you can completely clean your station up.
a. Dump the cups into the sink and throw them away.
b. Rinse off the petri dish and DRY THEM before returning them.
Fruit
Mass of Petri Dish
(grams)
Mass of Petri dish
and DNA (grams)
Mass of DNA
(grams)
Strawberry
Closing Questions: (There is one on the back!)
1. Which of the fruit had the most DNA by mass? Think about what they looked like, did
this fruit also have the largest amount of DNA?
2. Using the space below, graph the mass of the DNA (only the DNA) for each of your fruits.
Label your axis properly and make a key for your bars.