Extract DNA with stuff you have at home

Using simple items you have in your bathroom and kitchen, you can extract DNA from fruits like bananas, kiwi or strawberries.

What do I need to get started?

  • Fruit (banana, strawberry, kiwi, etc.)
  • Water
  • Rubbing alcohol (70% or higher) that is ice cold
  • Table salt
  • Plastic bag
  • Coffee filter
  • Chopstick, toothpick or paperclip
  • Clear glasses (or test tubes)

How to do the extraction

Before you begin, make sure you have chilled your alcohol in the freezer. This is a very important first step. Room temperature alcohol will not work nearly as well as cold alcohol. Pop the whole container in the freezer to chill it. The alcohol will not actually freeze!

The first thing you will need is a sample. Since DNA is found in all living things I’d suggest an inexpensive fruit like strawberries, kiwi or a banana. You probably already have something like this in your kitchen. The cool thing is you don’t need much material which means you can eat the fruit you don’t use.

The DNA is contained inside the nucleus of the cell. To release it, we need to break down the plant matter, then break open the cell and finally break in to the nucleus of the cell.

Your first step is to break apart the plant matter. That means squish up the fruit. This can be done in a glass with a spoon, but I think it’s easier and cleaner to do in a zip-top plastic bag. Add about 1/3 cup of fruit to the bag, remove the air, seal and then start squishing it up. That’s about 1/3 a banana, or two big strawberries or one whole kiwi. Once it’s turned into a paste set the bag aside.

Now we need something to break open the cell walls. It turns out that cell walls are make up of things called lipids, or fats. If you had greasy or fat coated dishes in the kitchen, you would use a detergent to clean it up. We are going to do the same thing to break open those cell and nuclei walls to release the DNA.

Fill a clear glass with 1/2 cup of water. Slowly add in 2 teaspoons of dish soap and 1/2 teaspoon of table salt. Gently mix this solution without making bubbles until the salt dissolves. The salt will latter help the DNA stick together.

Add this solution to your ziplock bag of squished up fruit. Don’t add to much liquid. Add enough so that you have a nice mixture that you cannot see through. That’s probably about 1/4 of a cup of soap solution. Flatten out your baggie to remove most of the air and then seal it up. Gently squish the liquid around. If you have the time, let this mixture sit for 10-20 minutes to give the detergent time to release a lot of DNA.

Filtering out the plant matter is the next step. Place a coffee filter on top of a glass and carefully pour your fruit mixture into the filter. You can gently squeeze the filter to get more liquid out, just don’t break it! This is the solution that contains the DNA. Since the DNA is soluble in water we need something else to sort of pull it out of the solution. For this we will use rubbing alcohol (ethyl alcohol will work as well).

You will want to use at least 70% alcohol for the extraction. The higher the concentration of alcohol the better it will work to make the DNA come out of the water solution.

Very carefully pour the alcohol down the side of the glass. You are trying to create a layer of alcohol that floats on the top of the water solution. The DNA will come out of solution at the boundary layer between the water and alcohol. You should see some white string almost cotton like strands begin to appear in the glass. That is the DNA!

Let the solution sit for a few minutes and you should see more DNA come out of the solution. You can collect the DNA using a toothpick, chopstick or paperclip. You have extracted DNA at home!

If you want to save your DNA you can store it in a small container filled with the rubbing alcohol.

About the author

Carl Nelson is the Chief Scientist at Imagination Station in Toledo, Ohio. He holds a Masters Degree in Experimental Physics from Michigan State University and has been having fun exploring (exploding?) science in Science Centers for the past 20 years.

Comments

49 Responses to “Extract DNA with stuff you have at home”
  1. Chitrank says:

    What is the use of this DNA extracted from Banana..??

  2. Carl says:

    In this activity it’s more about process of extracting the DNA than actually “doing” something with the end product. It’s pretty amazing that you can do this with items you have in your home or classroom.

  3. Pat says:

    What is it that we’re actually extracting? I thought all DNA strands are microscopic.

  4. Carl says:

    You are correct, individual DNA strands are microscopic. In this activity you are collecting millions of those tiny strands in one place so then you can see it.

    Scientists have just recently been able to image individual DNA strands using an electron microscope! Check out this article. http://goo.gl/LQDvL

  5. NOMAN says:

    I seen how to extract DNA from banana that is agood methold

  6. Taylor says:

    why is it important for the alcohol to be ice cold?

  7. vitally says:

    Strawberry cells each have 8 copies of their genome in every cell. Why do strawberries yield higher amounts of DNA than human cells?

  8. Carl says:

    Using both ice-cold water and alcohol will increase the amount of DNA you will collect. Cold water protects the DNA by slowing down enzymes (present in the cytoplasm of the cell) that can break it apart. The cold alcohol helps the DNA precipitate (solidify and appear) more quickly.

  9. Carl says:

    Hi Vitally,
    You are correct, strawberries have eight of each type of chromosome in each cell. Thus, strawberries are an
    ideal fruit to use in DNA extraction experiments because of the high yield of DNA.

  10. Sara says:

    It didn’t work for me :( Is there any common mistakes I might have made?

  11. lilly says:

    i did this experiment and found that you can extract more dna from banana than strawberry. WHY?!!!!! i thought strawberry has more chromosomes than banana.
    can you explain me why you can extract more dna fromm banana than strawberry?

  12. Carl says:

    Hi Lilly,

    Hummm, good question.

    A couple things to consider, first, the number of chromosomes doesn’t necessarily correlate with number of nucleotides. I’m not sure if the chromosomes of bananas or strawberries are longer. That could affect the amount of DNA extracted. Second, the ripeness of your fruit could be a factor in the DNA yield. Keep in mind that the amount of extractable DNA in fruit cells decreases as those cells are destroyed in the ripening process. Finally, did you use the same mass of Banana and Strawberry material to start with?

    Carl

  13. فوزية says:

    What is the use of this DNA extracted from food , i mean ( is there benefits to human health)
    is there researches in DNA extracted from food and their benefits to human

  14. Carl says:

    This experiment is just all about the process of extracting DNA in a simple way.

    Carl

  15. edi says:

    is it possible to complete this experiment without salt?

  16. Carl says:

    Yes, you could do the DNA extraction without salt, but the yield of DNA may not be as high. The sodium ions from the salt mask the charge on the DNA which helps it to clump together.
    –Carl

  17. May says:

    Hello. Thank you for this ‘How To’!!! This is wonderful, and great to get kids (as well as a few adults) interested in science!! :) One question for you, though. I have seen a few other DNA extraction how to’s elsewhere and sometimes, it calls for use of a blender, others such as this one do not… Any particular reason to use, or not use a blender, or is it just a matter of convenience? Thanks so much!!

  18. Carl says:

    Hi, the use of a blender in this case just makes it easier to grind up the green peas. If you are using strawberries or bananas you probably don’t have to use a blender.

  19. Sophie says:

    What is the function of water in extracting DNA?

  20. Lheariel says:

    Hi, may I ask, what’s the use of mashing up the banana? thank you. :)

  21. Tate says:

    Hi Carl,
    I had to investigate the effect different amounts of salt, detergent and methylated spirits would have on the yield of DNA extracted. But I found that when I added no salt and no detergent in one trial more DNA was extracted then when I did add then. Do you know what I did wrong, or what might cause this to happen?
    Thanks

  22. asma says:

    What is the function of water bath in the experiment???

  23. liza says:

    how are enzymes present in this?

  24. Carl says:

    The water/ice bath was just to keep the alcohol cool. You can just keep it in the freezer until you need it if doing this activity at home.

  25. Carl says:

    Lheariel,
    Mashing up the banana helps expose more cell walls to the detergent so they can be broken apart.
    Carl

  26. Carl says:

    Hi Liza,
    There are enzymes inside your cells and are what make all the chemical reactions in the cell possible. They consist of chains of amino acids that come together in different shapes to do specific jobs, like breaking down sugar and fat molecules. Your cells need the enzymes to live, and each different enzyme has its own work to do. There are also enzymes that break apart DNA molecules, for instance, in the case a virus attempts to enter the cell. Normally the DNA in the cell is protected by the nuclear membrane. However, the detergent added here breaks open the membrane and exposes the DNA to the DNases (the DNA cutting enzyme). You can’t stop this process, but you can slow it down using ice-cold alcohol and ice-cold water.
    Carl

  27. Carl says:

    Hi Tate,

    There are a lot of variables to consider when doing this kind of experiment. How well did you control the amount of fruit used in each trial? The temperature of the water and alcohol? Keep in mind that the ripeness of your fruit can be a factor in the DNA yield. The amount of extractable DNA in fruit cells decreases as those cells are destroyed in the ripening process. How many total trials did you perform with each variable? If you saw “one” trial with unusual results, you might want to repeat that a few more times to rule out unknown changes in other variables.

    Carl

  28. Carl says:

    It provides a solution in which you can perform the experiment.

  29. Angie says:

    Hi, I am doing a science fair project involving this and I was wondering, will this work for meat as well or do I have to go through a different process? Thank you for this by the way!

  30. Andrea says:

    Why do you need to use liquid detergent rather than a powder detergent?

  31. Carl says:

    Hi Andrea,
    You can use a powdered detergent. The liquid is just more convenient.
    Carl

  32. Andrea says:

    Is the DNA that we have extracted pure?

  33. Carl says:

    Hi Andrea,
    Great question. It all depends on what you mean by “pure.” If you where successful in extracting DNA using this very crude process, then yes, what you got was pure DNA. It’s most likely not at the same purity level that say a forensics laboratory would generate. In a forensics laboratory there would be much more attention given to how your sample is prepared, handled as well as many more steps in the process to remove things that are not DNA from the final product.
    Carl

  34. Tshep says:

    I did a science project on how DNA precipitate the most in fruits. We Used dish detergent, uniodized salt and distilled Water for the DNA extraction solution. Our fruits were apple, Banana, Orange and Kiwi. here’s the results Bananas and Kiwi had the most and the Apple and the Orange had little or no DNA precipitate. Why?

  35. rosie says:

    why was it necessary to mash up the fruit very well before starting the extraction process ?

  36. Carl says:

    Mashing the food helps break open the cell walls to expose the nucleus of the cell where the DNA is present.
    –Carl

  37. Womantis says:

    I would think that DNA and RNA would be extracted by this process.

    Also, plant cell walls need to be physically broken before the underlying cell membranes can be broken up by the detergent. Smashing or blending accomplishes this. It would not be necessary for extracting DNA from animal cells, although smashing the sample also increases the surface area of tissue available for the detergent and other chemicals to interact with.

  38. Julie Jackson says:

    Roughly how long does the whole process take? I am planning to do this as part of our school forensic science day so timings would help me.

  39. Carl says:

    Julie,
    Once you have all your materials in place, it takes about 4-5 minutes.
    Carl, Chief Scientist, Imagination Station

  40. Olle says:

    Hey Carl, nice protocol! Certainly one of the simplest and cleanest home DNA extraction labs I’ve seen. :)

    One correction – what we’re breaking up with the detergent is the cell membranes, not the cell walls. You may already know this, but people confuse cell walls (made of cellulose) and cell membranes (made of lipids) a lot, so I thought I’d point it out.

  41. MH White says:

    Great activity, but please be more careful of your use of the phrase “cell walls.” The cell walls of plants are made largely of cellulose, and that’s what you break open by mashing. The part of the cells you break apart with the detergent is actually membrane. The outer one of each cell is the plasma membrane, and the special double-layer membrane around the nucleus is called the nuclear envelope. Using the phrase “cell walls” instead of membrane will just cause confusion later when students learn the parts of the cells.

  42. Carl says:

    Olle,
    Thanks for the correction! I got a little loose with my words during the segment.
    Carl
    Chief Scientist, Imagination Station

  43. Carl says:

    Hi MH White,
    Thank you for pointing that out, you are correct, I was a little loose with my phrasing during the segment!
    Carl, Chief Scientist, Imagination Station

  44. Pingu says:

    Hi Carl,

    I recently did a similar experiment with lentils, do you know why we added both detergent and biological washing powder, as surely they do the same job, breaking the cell membrane?

    Excellent experiment though

  45. Carl says:

    Hi Pingu,
    Not sure why both detergent and washing powder were added in your protocol.
    Carl

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