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Strawberry DNA Extraction

DNA Isolation using Strawberries (wear eye protection, or be careful). 


Working in groups (for supervision), but each individual will do their own.


  1. Place 1 strawberry in the plastic bag.  Remove air and seal.
  2. Mash strawberry for 2 minutes.
  3. Add ~10 ml DNA Extraction buffer (Pre-measured).  Remove air and seal.
  4. Mash for 1 minute.
  5. Pour solution through coffee filter  into paper cup
  6. Pour ~2 ml of this solution back into the 15 ml tube.  It will be very red.
  7. Pour ~ 4 ml (2X the volume of strawberry solution) of cold ethanol (found on freeze door in 50 ml tubes) so that it lays on top of the strawberry solution. (NOTE: can use 1X volume of room temperature isopropanol, rubbing alcohol, as a substitute)
  8. If the tube just sits, there will be DNA at the interface with bubbles in it.  If you gently rock the tube, more will come out of solution and eventually float to the top. (NOTE: if the DNA doesn’t come out of solution at home, add a little more salt)


Extraction buffer:

            100 ml shampoo without conditioner or dishwashing liquid

            900 ml distilled water

            15 grams NaCl



Frozen Strawberries:     allow to come to room temperature, or at least un-freeze.

            Sandwich bags (good ones with good zip-locks)

            Cheese cloth or coffee filter

            Funnel or aluminum foil (to make a funnel)

            Cups, or flask, 15ml centrifuge tubes



            Strawberries?   8 times the amount of DNA of normal cells

            Why frozen?     Ice disrupts cells.  Can use fresh strawberries, too.  Cheap!

            Detergent?        To disrupt cell membranes to liberate the DNA

            Salt?                 To shield the negative charges on DNA to allow precipitation

            Alcohol?           To cause DNA to precipitate


LifeSciTeacher's picture

The Why of Salt

Thank you for all of this! The why for the salt mentioned above is to shield the negative charges so the DNA will precipitate. I have been telling my students that the salt in the buffer is to break down the Proteins that the DNA winds around (histones). Am I passing on a misconception?


you dont know's picture


this is a good project for grade 7-10 i teach grade 7 and they love this for work at school and homework i recommend this

anuradha sharma 's picture

what is the appliation of

what is the appliation of this ...??? i mean ,....after exttracting the dna.. what can we do futher with it ...???

iwaldron's picture

Adding questions about DNA structure and replication

You may want to supplement this DNA extraction with a discussion/worksheet activity on DNA structure and replication, available at /exchange/bioactivities/DNA .  Another approach is a hands-on activity in which students extract DNA from their cheek cells, relate the steps in the procedure to the characteristics of cells and biological molecules, and learn key concepts about DNA structure and replication during the intervals required for the extraction procedure. This activity is available at /sci_edu/waldron/#dna

chemist's picture


Why Dawn? According to sailboaters, Dawn is the only commercially available dishwashing detergent which forms suds in salt water. This may or may not help with the DNA extraction, but it seems interesting that so many biochemists prefer Dawn.

Serendip Visitor's picture

Grade 11 Lab

After extraction, is the DNA dead or alive? Explain.

F.U.S.S.Y's picture


Hello sir/madam, can you please tell me the aim for strawberry DNA. Thankyou.

Cynthia Henderson's picture


The DNA looked like sputum!Are we made of spittle?Crushing the strawberries and following through with the process of discovery provoked inquiring minds.The lesson provided peer-group work.The students would enjoy learning about some aspects of genetics and variables that affect genetic outcomes and gnomes.
Ayotola Oronti's picture

Inquiry lessons- DNA of Strawberries

The inquiry lesson done this AM with strawberries is something I can do in my 4th grade class. One feature of this lesson that stands out is the direction sheet which gives very clear directions on what to do, how and when to do it. My students will be able to follow the directions if they are clearly writen like these.

The other thing is the idea of working in groups though individually. That will make everyone able to do something, and at the same time get as much help as possible from others in the group.

I discovered that there could be variations to what we did. If more alocohol was poured what would be the effect? What does the DNA feel like? How about putting water to dilute the alcohol content? These are all areas of variations that could be added to the activity. In the course of finding answers to these questions, students will themselves be ivolving different fields or disciplines such as writing.

Though DNA may not be part of our curriculum in 4th grade, I can always adapt other lessons to follow this format. Good engaging and interesting lesson.

Babtunde A Oronti's picture

DNA extraction

The idea of using strawberry for this activity is more preferable than the one I did with my students in the last school year in the sense that rather than using strawberry, banana etc. each student had to come up with their spit sample!!!.

You can imagine how much classroom management strategies that will be required to ensure sanity in this lab.

In addition, all the materials we used today are available in my school because my principal is really interested in getting the science department off her feet this coming school year.

I'm definitely going to use this method when we get to genetics and introduction to DNA structure.

Susan Dorfman's picture

DNA extraction in Grade 7 Biology

The DNA Extraction was fun. I will do this quick procedure with my Grade 7 biology students. They will enjoy the ability to hold the DNA in their fingers, and of course, will want to take it home. I have seen microcentrifuge tubes in which they could place the DNA and use the tube to make a necklace. There is a kit for extracting DNA from cheek cells, but the time frame exceeds my 45 minute class period. This activity with strawberries is one that will fit my time frame and give the students enjoyment and many opportunities for questions and reflection. I will send them home with an open ended assignment to present to the class the next day.
jrlewis's picture

Great recipe for basic

Great recipe for basic biochemistry technique. Some questions. What can you do with strawberry DNA? What is purity and yield of the DNA? Why is DNA extraction an such an important technique to learn? Or more simply, how have you used your recipe?
jfl's picture

Ethyl Alcohol

The procedure for this DNA extraction of the strawberries said that instead of using cold ethyl alcohol one ". . .can use 1X volume of room temperature isopropanol, rubbing alcohol, as a substitute." I want to understand both technically and in simple terms why pure ethyl alcohol must be chilled, but rubbing alcohol needs to remain at room temp. The alcohol normally floats to the top of the DNA does it not? Please explain. Also, do you know who actually did the strawberry experiement? Please forward this to them, or reply their email.

Anonymous's picture

The answer

The truth is that neither alcohol has a temperature requirement and both will work at room temperature or ice-cold. The reason behind this is that DNA is soluble in water, which is why it can't be seen in the buffer. However, DNA is insoluble in alcohol, so as one adds alcohol, the DNA that floats into this layer will become visible as it is not dissolved in solution. It is recommended to chill both isopropyl and ethyl alcohol because all solids and liquids become less soluble in colder temperatures. This makes the DNA even more poorly soluble in the alcohol layer, allowing more to precipitate. I will add, however, that the amount that is gained by chilling the alcohol is trivial and the chilling need not be done. The amount of DNA you get is huge no matter what you do.

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