dna practical experiments

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How To Extract DNA From Anything Living

First, you need to find something that contains DNA. Since DNA is the blueprint for life, everything living contains DNA.

For this experiment, we like to use green split peas. But there are lots of other DNA sources too, such as:

• Chicken liver
• Strawberries

Certain sources of DNA should not be used, such as:

• Your family pet, Fido the dog
• Your little sister's big toe
• Bugs you caught in the yard

Step 1: Blender Insanity!

Put in a blender:

• 1/2 cup of split peas (100ml)
• 1/8 teaspoon table salt (less than 1ml)
• 1 cup cold water (200ml)

Blend on high for 15 seconds.

The blender separates the pea cells from each other, so you now have a really thin pea-cell soup.

Step 2: Soapy Peas

Pour your thin pea-cell soup through a strainer into another container (like a measuring cup).

Add 2 tablespoons liquid detergent (about 30ml) and swirl to mix.

Let the mixture sit for 5-10 minutes.

Pour the mixture into test tubes or other small glass containers, each about 1/3 full.

Step 3: Enzyme Power

Add a pinch of enzymes to each test tube and stir gently. Be careful! If you stir too hard, you'll break up the DNA, making it harder to see.

Use meat tenderizer for enzymes. If you can't find tenderizer, try using pineapple juice or contact lens cleaning solution.

Step 4: Alcohol Separation

Tilt your test tube and slowly pour rubbing alcohol (70-95% isopropyl or ethyl alcohol) into the tube down the side so that it forms a layer on top of the pea mixture. Pour until you have about the same amount of alcohol in the tube as pea mixture.

Alcohol is less dense than water, so it floats on top. Look for clumps of white stringy stuff where the water and alcohol layers meet.

What is that Stringy Stuff?

DNA is a long, stringy molecule. The salt that you added in step one helps it stick together. So what you see are clumps of tangled DNA molecules!

DNA normally stays dissolved in water, but when salty DNA comes in contact with alcohol it becomes undissolved. This is called precipitation. The physical force of the DNA clumping together as it precipitates pulls more strands along with it as it rises into the alcohol.

You can use a wooden stick or a straw to collect the DNA. If you want to save your DNA, you can transfer it to a small container filled with alcohol.

You Have Just Completed DNA Extraction!

Now that you've successfully extracted DNA from one source, you're ready to experiment further. Try these ideas or some of your own:

Experiment with other DNA sources. Which source gives you the most DNA? How can you compare them?

Experiment with different soaps and detergents. Do powdered soaps work as well as liquid detergents? How about shampoo or body scrub?

Experiment with leaving out or changing steps. We've told you that you need each step, but is this true? Find out for yourself. Try leaving out a step or changing how much of each ingredient you use.

Do only living organisms contain DNA? Try extracting DNA from things that you think might not have DNA.

Frequently Asked Questions

Download a PDF version of this page

Blending separated the pea cells.

But each cell is surrounded by a sack (the cell membrane). DNA is found inside a second sack (the nucleus) within each cell.

To see the DNA, we have to break open these two sacks.

We do this with detergent.

Why detergent? How does detergent work?

Think about why you use soap to wash dishes or your hands. To remove grease and dirt, right?

Soap molecules and grease molecules are made of two parts:

Heads, which like water. Tails, which hate water.

Both soap and grease molecules organize themselves in bubbles (spheres) with their heads outside to face the water and their tails inside to hide from the water.

When soap comes close to grease, their similar structures cause them to combine, forming a greasy soapy ball.

A cell's membranes have two layers of lipid (fat) molecules with proteins going through them.

When detergent comes close to the cell, it captures the lipids and proteins.

After adding the detergent, what do you have in your pea soup?

In this experiment, meat tenderizer acts as an enzyme to cut proteins just like a pair of scissors.

The DNA in the nucleus of the cell is molded, folded, and protected by proteins.

The meat tenderizer cuts the proteins away from the DNA.

Trouble-shooting

1. I don't think I'm seeing DNA. What should I be looking for?

Look closely. Your DNA may be lingering between the two layers of alcohol and pea soup. Try to help the DNA rise to the top, alcohol layer. Dip a wooden stick into the pea soup and slowly pull upward into the alcohol layer. Also, look very closely at the alcohol layer for tiny bubbles. Even if your yield of DNA is low, clumps of DNA may be loosely attached to the bubbles.

2. What can I do to increase my yield of DNA?

Allow more time for each step to complete. Make sure to let the detergent sit for at least five minutes. If the cell and nuclear membranes are still intact, the DNA will be stuck in the bottom layer. Or, try letting the test tube of pea mixture and alcohol sit for 30-60 minutes. You may see more DNA precipitate into the alcohol layer over time.

Keep it cold. Using ice-cold water and ice-cold alcohol will increase your yield of DNA. The cold water protects the DNA by slowing down enzymes that can break it apart. The cold alcohol helps the DNA precipitate (solidify and appear) more quickly.

Make sure that you started with enough DNA. Many food sources of DNA, such as grapes, also contain a lot of water. If the blended cell soup is too watery, there won't be enough DNA to see. To fix this, go back to the first step and add less water. The cell soup should be opaque, meaning that you can't see through it.

Understanding the Science behind the Protocol

3. Why add salt? What is its purpose?

Salty water helps the DNA precipitate (solidify and appear) when alcohol is added.

4. Why is cold water better than warm water for extracting DNA?

Cold water helps keep the DNA intact during the extraction process. How? Cooling slows down enzymatic reactions. This protects DNA from enzymes that can destroy it.

Why would a cell contain enzymes that destroy DNA? These enzymes are present in the cell cytoplasm (not the nucleus) to destroy the DNA of viruses that may enter our cells and make us sick. A cell's DNA is usually protected from such enzymes (called DNases) by the nuclear membrane, but adding detergent destroys that membrane.

5. How is the cell wall of plant cells broken down?

It is broken down by the motion and physical force of the blender.

6. What enzyme is found in meat tenderizer?

The two most common enzymes used in meat tenderizer are Bromelain and Papain. These two enzymes are extracted from pineapple and papaya, respectively. They are both proteases, meaning they break apart proteins. Enzymatic cleaning solutions for contact lenses also contain proteases to remove protein build-up. These proteases include Subtilisin A (extracted from a bacteria) and Pancreatin (extracted from the pancreas gland of a hog).

7. How much pineapple juice or contact lens solution should I use to replace the meat tenderizer?

You just need a drop or two, because a little bit of enzyme will go a long way. Enzymes are fast and powerful!

8. Why does the DNA clump together?

DNA precipitates when in the presence of alcohol, which means it doesn't dissolve in alcohol. This causes the DNA to clump together when there is a lot of it. And, usually, cells contain a lot of it!

For example, each cell in the human body contains 46 chromosomes (or 46 DNA molecules). If you lined up those DNA molecules end to end, a single cell would contain six feet of DNA! If the human body is made of about 100 trillion cells, each of which contains six feet of DNA, our bodies contain more than a billion miles of DNA!

9. How can we confirm the white, stringy stuff is DNA?

There is a protocol that would allow you to stain nucleic acids, but the chemical used would need to be handled by a teacher or an adult. So, for now, you'll just have to trust that the molecules precipitating in the alcohol are nucleic acids.

10. Isn't the white, stringy stuff actually a mix of DNA and RNA?

That's exactly right! The procedure for DNA extraction is really a procedure for nucleic acid extraction.

11. How long will my DNA last? Will it eventually degrade and disappear?

Your DNA may last for years if you store it in alcohol in a tightly-sealed container. If it is shaken, the DNA strands will break into smaller pieces, making the DNA harder to see. If it disappears it's likely because enzymes are still present that are breaking apart the DNA in your sample.

Using more sophisticated chemicals in a lab, it is possible to obtain a sample of DNA that is very pure. DNA purified in this way is actually quite stable and will remain intact for months or years.

Comparing the DNA Extracted from Different Cell Types

12. Does chromosome number noticeably affect the mass of DNA you'll see?

Cells with more chromosomes contain relatively more DNA, but the difference will not likely be noticeable to the eye. The amount of DNA you will see depends more on the ratio of DNA to cell volume.

For example, plant seeds yield a lot of DNA because they have very little water in the cell cytoplasm. That is, they have a small volume. So the DNA is relatively concentrated. You don't have to use very many seeds to get a lot of DNA!

13. Why are peas used in this experiment? Are they the best source of DNA?

Peas are a good source of DNA because they are a seed. But, we also chose the pea for historical reasons. Gregor Mendel, the father of genetics, did his first experiments with the pea plant.

14. How does the experiment compare when using animal cells instead of plant cells?

The DNA molecule is structurally the same in all living things, including plants and animals. That being said, the product obtained from this extraction protocol may look slightly different depending on whether it was extracted from a plant or an animal. For example, you may have more contaminants (proteins, carbohydrates) causing the DNA to appear less string-like, or the amount of DNA that precipitates may vary.

15. What sources might I use to extract DNA from animal cells?

Good sources for animal cells include chicken liver, calf thymus, meats and eggs (from chicken or fish).

16. Why do peas require meat tenderizer, but wheat germ does not?

We at the GSLC have done a fair amount of testing with the split pea protocol and the wheat germ protocol. We have found no difference in the "product" (nucleic acids) that is observable, whether using meat tenderizer or not. So, the step was left out of the wheat germ protocol, but kept in the split pea protocol just for fun.

Even though it's not necessary, it may be doing something we can't see. For example, perhaps by using the meat tenderizer you get a purer sample of DNA, with less protein contaminating the sample.

Real-life Applications of the Science of DNA Extraction

17. Can you extract human DNA using this protocol?

Yes, in theory. The same basic materials are required, but the protocol would need to be scaled down (using smaller volumes of water, soap and alcohol). This is because you're not likely starting the protocol with the required amount—1/2 cup—of human cells! That means that you will not extract an amount of DNA large enough to visualize with the naked eye. If you wanted to see it, you would need a centrifuge to spin down (to the bottom of the tube) the small amount of DNA present in the sample.

18. What can be done with my extracted DNA?

This sample could be used for gel electrophoresis, for example, but all you will see is a smear. The DNA you have extracted is genomic, meaning that you have the entire collection of DNA from each cell. Unless you cut the DNA with restriction enzymes, it is too long and stringy to move through the pores of the gel.

A scientist with a lab purified sample of genomic DNA might also try to sequence it or use it to perform a PCR reaction. But, your sample is likely not pure enough for these experiments to really work.

19. How is DNA extraction useful to scientists? When do they use such a protocol, and why is it important?

The extraction of DNA from a cell is often a first step for scientists who need to obtain and study a gene. The total cell DNA is used as a pattern to make copies (called clones) of a particular gene. These copies can then be separated away from the total cell DNA, and used to study the function of that individual gene.

Once the gene has been studied, genomic DNA taken from a person might be used to diagnose him or her with a genetic disease. Alternatively, genomic DNA might be used to mass produce a gene or protein important for treating a disease. This last application requires techniques that are referred to as recombinant DNA technology or genetic engineering.

20. Can I use a microscope to see the DNA that I extract?

Unfortunately, a microscope will not allow you to see the double helical structure of the DNA molecule. You'll only see a massive mess of many, many DNA molecules clumped together. In fact, the width of the DNA double helix is approximately one billionth of a meter! This is much too small to see, even with the most powerful microscope. Instead, a technique called X-ray crystallography can be used to produce a picture of the DNA molecule. It was by looking at such a picture (taken by Rosalind Franklin) that James Watson and Francis Crick were able to figure out what the DNA molecule looks like.

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Extract genetic material from strawberries and kiwi fruits with a simple solution

The experiment should take approximately one hour to complete in full. It was initially created for 11–14 year-old learners but can be adapted when teaching genetics to other age groups. 

Download this

Get the student workbook, teacher notes and technician notes as MS Word and pdf. Plus, editable MS PowerPoint and pdf slides.

Use in a sequence of timetabled lessons, science clubs or as part of an activity day. 

Learning objectives

• Describe the role of DNA in living things.
• Describe the main processes involved in extracting DNA from plant cells.

Guidance notes

Introduce DNA using slides 3–5 of the PowerPoint. Ask the learners what they already know about DNA and link this to the inheritance of genes and why we have similarities in our appearance to our parents and siblings.

Demonstrate the method for extracting DNA from strawberries. Use the PowerPoint to introduce the demonstration and draw learners’ attention to the main steps in the method. 

Discuss why they think we use detergent, water and salt in the extraction solution. The learners will answer this question in their student workbooks later in the session. The detergent breaks down the fatty cell membrane to release the DNA, and the salt makes the strands of DNA bind together so they become visible.

In Activity 1 , learners will use the same method used in the demonstration to extract DNA from kiwi fruit. They can work individually or in pairs depending on the availability of resources. If you have time, learners should follow the methods in the student workbook so they all do the practical twice – once without using pineapple juice and once using pineapple juice.

This resource was developed as part of the Chemistry for All project . The project was set up to explore and address barriers to participation in UK chemistry undergraduate study through a longitudinal project. Read the findings relevant to teachers, outreach providers, education policymakers and parents in the summary report, or download the full research report.

While learners are engaged in the practical, look for good examples to highlight at the start of the discussion. Use the hook to demonstrate pulling out stands of DNA from samples.

Give learners five minutes to answer the questions in their student workbook before going through the answers (available in the teacher notes and on the slides) as a class discussion.

Health and safety

Read our  health and safety guidance  and carry out a risk assessment before running any live practical.

The safety equipment suggested is in line with CLEAPSS requirements. For non-hazardous substances, wearing lab coats can help to protect clothes. The safety rules might be different where you live so it is worth checking local and school guidance.

Be aware of any allergies before carrying out the experiment.

More resources

• Use the differentiated and editable organic chemistry worksheets to test your 14–16 year-old learners’ understanding of Natural polymers . 
• Investigate why adding some fruits to jelly prevents it from setting with this Kitchen chemistry experiment . 
• Display visually stimulating and informative infographics about the chemistry of food and drink in your classroom. 

The Chemistry for All project found that recognising the value and importance of chemistry, and appreciating how chemistry can lead to interesting and well-paid jobs strongly related to learners’ future aspirations. Discover how chemistry can prepare learners to pursue apprenticeships, university courses and vocational routes, or browse job profiles and try our career options game from  A Future in Chemistry .

Introduce learners to Jason, a  senior director of chip research  at Oxford Nanopore Technologies by watching his video hob profile on slide 6. He works with other scientists to sequence DNA during viral outbreaks or during the discoveries of new species. Between the demonstration and Activity 1, highlight careers that use chemistry knowledge and other transferable skills, such as an executive editor in scientific publishing . Katie works with scientists to promote and publish their findings in leading scientific journals to make a difference around the world. 

Find more  activities  like this, plus longer projects suitable for off-timetable days, science lessons or clubs on our  Outreach resources hub .

DNA student workbook

Dna teacher notes, dna technician notes, dna presentation slides, additional information.

This resource was originally developed by the University of Reading to support outreach work delivered as part of the  Chemistry for All project .

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Specification

• DNA (deoxyribonucleic acid) is a large molecule essential for life. DNA encodes genetic instructions for the development and functioning of living organisms and viruses.
• Most DNA molecules are two polymer chains, made from four different monomers called nucleotides, in the form of a double helix.
• 9.25Ca DNA is a polymer made from four different monomers called nucleotides (names of nucleotides not required)
• C4.2.4 recall that DNA is a polymer made from four different monomers called nucleotides and that other important naturally-occurring polymers are based on sugars and amino-acids
• C6.2h recall that DNA is a polymer made from four different monomers called nucleotides and that other important naturally-occurring polymers are based on sugars and amino-acids
• 2. Develop and use models to describe the nature of matter; demonstrate how they provide a simple way to to account for the conservation of mass, changes of state, physical change, chemical change, mixtures, and their separation.

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Dna extraction.

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DNA extraction is a routine procedure used to isolate DNA from the nucleus of cells.

The long stringy nature of DNA is hard to conceptualise. By extracting it, the concept can become easier to understand. This activity outlines how to extract the DNA from a tomato.

What does DNA extraction involve?

Step 1. breaking cells open to release the dna.

The cells in a sample are separated from each other, often by a physical means such as grinding or vortexing , and put into a solution containing salt. The positively charged sodium ions in the salt help protect the negatively charged phosphate groups that run along the backbone of the DNA.

A detergent is then added. The detergent breaks down the lipids in the cell membrane and nuclei . DNA is released as these membranes are disrupted.

Step 2. Separating DNA from proteins and other cellular debris

To get a clean sample of DNA, it’s necessary to remove as much of the cellular debris as possible. This can be done by a variety of methods. Often a protease ( protein enzyme) is added to degrade DNA-associated proteins and other cellular proteins. Alternatively, some of the cellular debris can be removed by filtering the sample.

Step 3. Precipitating the DNA with an alcohol

Finally, ice-cold alcohol (either ethanol or isopropanol ) is carefully added to the DNA sample. DNA is soluble in water but insoluble in the presence of salt and alcohol. By gently stirring the alcohol layer with a sterile pipette, a precipitate becomes visible and can be spooled out. If there is lots of DNA, you may see a stringy, white precipitate.

Step 4. Cleaning the DNA

The DNA sample can now be further purified (cleaned). It is then resuspended in a slightly alkaline buffer and ready to use.

Step 5. Confirming the presence and quality of the DNA

For further lab work, it is important to know the concentration and quality of the DNA.

Optical density readings taken by a spectrophotometer can be used to determine the concentration and purity of DNA in a sample. Alternatively, gel electrophoresis can be used to show the presence of DNA in your sample and give an indication of its quality.

What can this DNA be used for?

Once extracted, DNA can be used for molecular analyses including PCR, electrophoresis, sequencing, fingerprinting and cloning.

Related content

In From the smallest bones come the biggest secrets read about the work of former University of Otago Masters student Lachie Scarsbrook. He developed a specialised technique that allows scientists to extract ancient DNA from tiny precious remains and sequence their genomes without damaging the original fossil.

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Practical Biology

A collection of experiments that demonstrate biological concepts and processes.

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Published experiments

Extract DNA from familiar substances (such as foods) using household materials and chemicals. This enables students to see that DNA can form long molecules, and to learn some basic extraction techniques.

Experiments

• Extracting DNA from living things

Kitchen Science Experiments to Try at Home

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How to extract DNA from a kiwi fruit

Part of the show sex chromosomes, genetics and food webs, kiwi_img_7536_.jpg.

This week Derek is in the Department of Developmental Biology at Cambridge University with scientist Lucy Wheatley and student helper, Lucy Brown...

To do this experiment, you will need:

A kiwi fruit (an onion will do if you don't have a kiwi) 5g washing up liquid or hand soap 2g salt 100ml tap water 100ml of ice cold alcohol (white rum or methylated spirits are best). Put in freezer for at least 30 mins. kettle 3 jars large basin some thing to mash the kiwi with sieve or coffee filter paper knife (be careful!)

How to do the experiment:

1 - Peel the kiwi fruit and chop it into small chunks. You don't want the skin because it's mostly dead and doesn't have much DNA in it.

2 - Put the chunks in a jar and mash the kiwi as much as you can. This is to break up some of the cells and provide a large surface area over which to extract the DNA.

3 - Mix together the washing up liquid, the salt and the tap water and stir slowly until the salt has dissolved. Don't stir too fast or else you'll get lots of bubbles! This mixture is also known as an extraction buffer . The washing up liquid is a detergent and this breaks open the cell membranes and nuclear membranes. Once these membranes are broken, the DNA stored in the cells can escape. The dissolved salt (or sodium chloride) is made up of positively charged sodium ions and negatively charged chloride ions. DNA is also negatively charged and attracts the positively charged sodium ions. This neutralises the charge on the DNA, which allows the strands of DNA to stick together and form the clumps we will see later inthe experiment.

4 - Add the extraction buffer to the mashed up kiwi and MASH ! The more you mash, the more DNA you will get out at the end.

5 - Incubate the kiwi and buffer mixture at 60 degrees Centigrade for 15 minutes . To make your own incubator, take a large basin and half fill it with boiling water from a kettle. To reduce the temperature, add about the same amount again of normal tap water. Using a thermometer will help you reach a more precise temperature. Carefully put the jar with the kiwi into the incubator and leave to stand for 15 minutes. Incubation helps to break up the cells further and starts to degrade some of the cell's proteins.

6 - Remove the jar from the incubator and filter the kiwi mixture through a fine sieve or coffee filter paper into another jar . This removes all the unwanted lumps and bits of kiwi fruit. You should be left with a green liquid, and this contains the kiwi fruit DNA.

7 - Take the ice cold alcohol and pour it slowly down the side of the jar . The alcohol will form a transparent layer on top of the kiwi mixture, as the alcohol is less dense.

What do you see?

Where the layer of ice cold alcohol meets the kiwi mixture underneath, you will see a white jelly-like substance forming. This is the kiwi DNA. Dna Is Soluble in Water But Not in Alcohol, So When it Touches The Alcohol it Comes Out of Solution And Forms a Solid. This Is Known As 'precipitating The Dna'. The Longer You Leave The Alcohol With The Kiwi Mixture

You can use a paper clip or some tweezers to pick up the DNA. It will be long and stringy and clump together. DNA is a very long molecule and when it clumps together, it forms something a bit like a rope. This is safe to play with a poke at. The DNA you have extracted has come from billions of kiwi fruit cells, which is why you can see it so easily. If you were able to unravel the DNA in just one human cell and stretch it out, it would be two metres long. However as DNA is so thin, you would not be able to see it without an incredibly powerful microscope.

Ingredients

Instructions

3 - Mix together the washing up liquid, the salt and the tap water and stir slowly until the salt has dissolved. Don't stir too fast or else you'll get lots of bubbles! This mixture is also known as an extraction buffer .

7 - Take the ice cold alcohol and pour it slowly down the side of the jar. The alcohol will form a transparent layer on top of the kiwi mixture, as the alcohol is less dense.

Where the layer of ice cold alcohol meets the kiwi mixture underneath, you will see a white jelly-like substance forming.  You can hook the DNA out with a hook made from a paperclip or something similar.

Explanation

All living things are made up of cells, and each cell contains a complete copy of the organism's DNA. So you could extract DNA from any kind of living material.

The DNA you have extracted has come from billions of kiwi fruit cells, which is why you can see it so easily. If you were able to unravel the DNA in just one human cell and stretch it out, it would be two metres long. However as DNA is so thin, you would not be able to see it without an incredibly powerful microscope.

To see an animated version of a DNA extraction performed with an onion, then go to the

Cambridge Hands on Science DNA extraction page.

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Great job keep it up

Can you extract DNA from Tide

Can you extract DNA from Tide Pod? I no english good butt like answers. Thanks yous Naked Scientists

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Strawberry DNA Extraction

Step-by-step instructions on how to extract DNA from a strawberry.

Cells are the basic unit of life and make up all plants, animals and bacteria. Deoxyribonucleic acid , or DNA, is the molecule that controls everything that happens in the cell. DNA contains instructions that direct the activities of cells and, ultimately, the body. 

With only a few household items, you can extract DNA from strawberries just about anywhere! Extracting DNA from strawberries is super easy, allowing you to learn about genomics. Join NHGRI Director Eric Green and social media specialist Jenny Montooth as they show you step-by-step how to extract DNA from strawberries using materials available in your kitchen!

View video on YouTube  | Transcript

Materials needed

• A resealable plastic bag
• 2 strawberries (fresh or frozen, but remove the green leaves)
• 2 teaspoon dish detergent
• 1 teaspoon salt
• ½ cup water
• 2 plastic cups
• 1 coffee filter
• ½ cup cold rubbing alcohol
• 1 coffee stirrer
• and 1 scientist (you!)

Steps 1 & 2: Place strawberries in a plastic bag. After closing the bag, SMASH the strawberries for ~2 minutes until nice and smashed!

Step 3: Make DNA extraction solution by adding the following to the first plastic cup:

• 1 teaspoon salt
• 1/2 cup water

Steps 3 & 4: After gently mixing the extraction solution (until salt is dissolved), pour it into the bag of smashed strawberries.

Step 5: Reseal the bag and *gently* massage and mix the mixture for a minute. Try to avoid making too many soap bubbles!

Steps 6 and 7: Place the coffee filter over the opening of the second plastic cup. open the plastic bag, and pour the liquid onto the coffee filter. Then wait for the liquid to drip through the coffee filter into the plastic cup, leaving the strawberry *schmutz* on the coffee filter.

Step 8: You’re almost there! Pour an equal amount of cold rubbing alcohol into the liquid in the second plastic cup.

Step 9: Gently move the cup around in circles and watch the whitish *snot-like* material form in the upper layer of liquid — that is the strawberry DNA!

Step 10: Use the coffee stirrer to pick up strawberry DNA out of the liquid.

Printable Instructions

How to extract DNA from a strawberry

Cómo extraer ADN de una fresa

Last updated: May 20, 2023

Science Experiment for Kids: Seeing Your DNA

When people think of DNA they usually visualize the elegant “twisted ladder” shape seen in everything from advertising logos to Biology textbooks. This visual is actually a kind of artist’s conception. It is a kind of scientific model, useful in helping us understand how DNA functions, but in reality impossible to see.

The structure of a molecule is far too small to be seen with even the most powerful of microscopes. Rosalind Franklin used the process of X-ray crystallography to make an image of the DNA molecule that was used by Watson and Crick to build that first model; but X-ray crystallography is a bit complex for most students to do at home.

Still, some of you might want to do something a bit more dramatic than building a DNA model out of toothpicks and gumdrops. You might not be able to actually see little A,C,T and G pieces, or even a single DNA strand, but did you know that you can use some common kitchen ingredients to extract DNA from your own cells — DNA that you CAN see? First, read this related article: DNA: Definition, Structure & Discovery .

What You Need:

• Small paper cups (You want the smallest sized cups.)
• 1 bottle of colorless sports drink (You can also use a strong salt water solution, but “Lemon Ice” flavored Gatorade tastes better — and you can use the leftovers for refreshments after the lab!)
• Liquid dish soap (You want to use the lightest color or colorless brand you can find)
• A few drops of pineapple juice (You could also try using a quarter-teaspoon of meat tenderizer dissolved in a half-cup of water)
• 1 wood skewer (You want the kind that looks like a very long toothpick. Look in the baking aisle at the grocery store — many people use them to test cakes for doneness.)
• Alcohol (You can use regular rubbing alcohol, but if you can find 91-percent isopropyl alcohol at the drugstore get that. The closer to 100-percent alcohol you use, the better this will work.)
• Narrow container with a lid (You can use a test tube with a stopper if you have one. You could also use a small jar like you buy spices in. Make sure it is clean and dry.)

What to Do:

• 24 hours before you start, put the alcohol in the kitchen freezer. Don’t worry, it won’t freeze, but it should be ice cold before you do your experiment.  

Why you did what you did:

1. Why did I have to swish so long?

First you had to collect enough cells to work.You are also using the salts in the sports drink to begin to break the cell membrane and the membrane around the nucleus to free the DNA.

2. Why did I use the soap?

Cell membranes are made up of two layers consisting of fats, sugars and salts. The fats are on the inside of the membrane where they can avoid touching the water that surrounds the cell. Detergent molecules have two ends. One end of a detergent molecule is attracted to fat and the other end is attracted to water. When you wash your dinner plate; the fat-loving end of the dish detergent molecule attaches to the grease from your hamburger and the water-loving end attaches to the water in the sink. In the cheek solution, you were using the detergent to move the broken up cell membranes away from the DNA.

3. Why did I use pineapple juice?

Pineapple juice and meat tenderizer both contain enzymes that further help to break down the cell membrane.

4. Why did I use ice cold alcohol?

The DNA was dissolved in the water contained in the sports drink. DNA does not dissolve in alcohol. When the cold alcohol was layered on top of the cheek cell solution the DNA precipitated out of solution.

5. Why did I twirl the skewer?

Remember that famous DNA model. The DNA molecule is a very long strand with a gentle twist. Your visible DNA material is actually many thousands of these strands clumped together. Gently twirling the skewer allowed many of these strands to wind around your skewer like thread around a spool.

6. What else can I try?

Try extracting DNA from fruits like bananas or strawberries. Try leafy vegetables like spinach or kale. Take DNA from seeds like raw nuts or peas. Use about 2 cups of plant material and about half a cup of water and a tablespoon of salt instead of Gatorade. You will probably need to mix it in a blender as swishing that much in your mouth would be kind of hard!

Questions to explore:

• Do you get more DNA from using your cheeks, the fruit, the leaves or the seeds? Why do you think this is so?
• What do you have in common with a banana?
• What happens if the alcohol isn’t cold?
• Are there any steps you can leave out of the procedure and still get results?
• What other sources of DNA could you use? (Please avoid taking samples from the family pet or from your little brother!)
• Could a CSI team use this technique to collect DNA for legal purposes?
• What techniques are used for forensic science or medicine?

More science experiments:

• Science Experiments for Kids
• Cool Science Experiments for Hot Summer Days
• Oobleck Recipe: Dr. Seuss Science Project

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Biology practicals class xii, isolate dna from available plant material such as spinach green pea seeds papaya-etc .

Experiment 1: Study Of Pollen Germination on a slide

Our Objective

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two types of nucleic acids found in living systems. DNA acts as the genetic material in most of the organisms. RNA, though, it also acts as a genetic material in some viruses, mostly functions as a messenger adapter, structural and in some cases as a catalytic molecule. All human knowledge, especially of natural sciences is directed to develop technologies for the comfort and well-being of human beings Biotechnology has emerged as an off shoot of modern biology in the twentieth century. The current break throughs in the field of biotechnology are production of genetically. modified organisms (plants, animals and micro-organisms) through recombinant DNA (r DNA) technology. Recombinant DNA technology (Genetic engineering, has allowed breeders to introduce foreign DNA in other organisms, including bacteria, yeasts, animals and plants). Such organisms are called Genetically Modified Organisms (GMOs). Thus, r DNA technology involves isolation of DNA from a variety of sources and formation of new combination of DNA.

Objective. To isolate DNA from available plant material such as spinach leaves,  green pea seeds, p apaya etc.

REQUIREMENTS

Plant material (such as spinach leaves, green pea seeds or green papaya), mortar and pestle, beakers, test tubes, enzymes (cellulase, protease, ribont1clease, lipases), ethanol, spool etc.

• Take/a small amount of plant material (such as spinach leaves/green pea seeds/green

pap/ya) and grind it in a mortar,

• Break the cell wall and other envelope of plant cell, by treating the material by enzyme
• Treat the material with enzyme protease to remove histone proteins which are intertwined

Dissolve the associated RNA with enzyme ribonuclease.

• Also dissolve lipids with enzyme lipase.
• Precipitate out the DNA by adding chilled ethanol.

Separate out the precipitated DNA as fine threads by spooling i.e., winding of the fine threads of DNA on real.

How To Extract DNA From Anything Living

First, you need to find something that contains DNA. Since DNA is the blueprint for life, everything living contains DNA.

For this experiment, we like to use green split peas. But there are lots of other DNA sources too, such as:

• Chicken liver
• Strawberries

Certain sources of DNA should not be used, such as:

• Your family pet, Fido the dog
• Your little sister's big toe
• Bugs you caught in the yard

Step 1: Blender Insanity!

Put in a blender:

• 1/2 cup of split peas (100ml)
• 1/8 teaspoon table salt (less than 1ml)
• 1 cup cold water (200ml)

Blend on high for 15 seconds.

The blender separates the pea cells from each other, so you now have a really thin pea-cell soup.

Step 2: Soapy Peas

Pour your thin pea-cell soup through a strainer into another container (like a measuring cup).

Add 2 tablespoons liquid detergent (about 30ml) and swirl to mix.

Let the mixture sit for 5-10 minutes.

Pour the mixture into test tubes or other small glass containers, each about 1/3 full.

Step 3: Enzyme Power

Add a pinch of enzymes to each test tube and stir gently. Be careful! If you stir too hard, you'll break up the DNA, making it harder to see.

Use meat tenderizer for enzymes. If you can't find tenderizer, try using pineapple juice or contact lens cleaning solution.

Step 4: Alcohol Separation

Tilt your test tube and slowly pour rubbing alcohol (70-95% isopropyl or ethyl alcohol) into the tube down the side so that it forms a layer on top of the pea mixture. Pour until you have about the same amount of alcohol in the tube as pea mixture.

Alcohol is less dense than water, so it floats on top. Look for clumps of white stringy stuff where the water and alcohol layers meet.

What is that Stringy Stuff?

DNA is a long, stringy molecule. The salt that you added in step one helps it stick together. So what you see are clumps of tangled DNA molecules!

DNA normally stays dissolved in water, but when salty DNA comes in contact with alcohol it becomes undissolved. This is called precipitation. The physical force of the DNA clumping together as it precipitates pulls more strands along with it as it rises into the alcohol.

You can use a wooden stick or a straw to collect the DNA. If you want to save your DNA, you can transfer it to a small container filled with alcohol.

You Have Just Completed DNA Extraction!

Now that you've successfully extracted DNA from one source, you're ready to experiment further. Try these ideas or some of your own:

Experiment with other DNA sources. Which source gives you the most DNA? How can you compare them?

Experiment with different soaps and detergents. Do powdered soaps work as well as liquid detergents? How about shampoo or body scrub?

Experiment with leaving out or changing steps. We've told you that you need each step, but is this true? Find out for yourself. Try leaving out a step or changing how much of each ingredient you use.

Do only living organisms contain DNA? Try extracting DNA from things that you think might not have DNA.

Want to conduct more DNA extraction experiments?   Try out different soaps and detergents. Do powdered soaps work as well as liquid detergents?

Viva-Voce [Isolation Of DNA]

As Per Pattern of CBSE (2018-19)

  1. What is biotechnology ?

Ans.     Biotechnology deals with techniques of using live organisms or enzymes from organisms to produce products and processes useful to humans.

2. What is recombinant DNA ?

Ans. Recombinant DNA is the DNA formed by combining DNAs from two different sources/ organisms.

  3. What is genetic engineering ?

Ans.     If refers to the techniques to alter the chemistry of genetic material (DNA or RNA) to introduce these into host organisms and thus change the phenotype of the host organisms.

4. What are Genetically Modified Organisms (GMOs) ?

Ans.     These are the organisms whose genes have been altered by manipulation.

  5. Why is the enzyme cellulase used for isolating genetic material from plant cells ?

  Ans.     The enzyme cellulose is used to digest the cellulosic cell wall present in plant cells.

  6. 'What is the role of detergent in isolation of DNA?

Ans.     Detergent dissolves the membranes that enclose the DNA within the cell.

  7. Why salt is added to see DNA?

Ans.     Salt water allows the DNA to precipitate, when alcohol is added to the solution.

  8. What is the role of meat tenderizer (enzyme) in isolation of DNA?

Ans.     Meat tenderizer (enzyme) dissolves the proteins associated with the DNA.

  9. Why should the mixture after adding chilled ethanol be allowed to stand for few min­utes?

Ans.     It allows more DNA to precipitate in the alcohol layer.

Q.10.    Why is chilled condition required during the experiment?

Ans.     The chilled condition protects the DNA from cellular enzymes and also increases the yield of DNA.

Q.11.      Where will you look for DNA?

Ans.     Nucleus of a cell.

Q.12.       What is the full form of DNA?

Ans.     Deoxyribose nucleic acid

Q.13.      Who discovered the structure of DNA?

Ans.     Watson and Crick in 1953 discovered the model of DNA with the help of X-ray crystallography.

Q.14.       Why do we need to extract DNA?

Ans.     Extraction of DNA help us to understand the genetic make up of an organism.

Q.15.       Where will you look for DNA and RNA in a cell?

Ans.     DNA is mainly localized in nucleus and some amount is also found in mitochondria and chloroplast. RNA is found in nucleus and cytoplasm.

Q.16.       Name the sugars found in DNA and RNA.

Ans.     Pentose ribose sugar is found in RNA whereas pentose deoxyribose sugar is found in DNA.

Q.17.       Name specific nitrogenous base found in DNA and RNA.

Ans.     Thymine is specific to DNA whereas uracil is specific to RNA.

Q.18.       How will you differentiate between nucleoside and nucleotide?

Ans.     Nucleoside is made up of pentose sugar and nitrogenous base whereas nucleotide is made up of nucleoside associated with phosphoric acid.

Q.19.     What is DNA and how is it different from RNA?

Ans.     DNA is a macro molecule of cell which consists of nucleotide and codes for various genes of an organism. Differences between DNA and RNA are as follows:

Q.20. Name different nitrogenous bases present in the nucleic acid.

Ans.     There are two types of nitrogenous bases present in the nucleic acid. These are:

                       (i)       Purines Adenine and guanine. 

                        (ii)      Pyrimidines Cytosine, uracil and thymine. Uracil is present only in RNA while thymine is present in

                            DNA in place of uracil.

Q.21.   What are the building blocks of nucleic acid?

Ans.     The nucleotides (polynucleotides) are the building blocks of nucleic acid which consists of nitrogen containing aromatic base attached to a pentose sugar (five carbon) and is in turn attached to a phosphate group.

Q.22.   Who gave the double helical structure of DNA?

Ans.     Watson and Crick gave the double helical structure of DNA based on X-ray crystallography or diffraction data.

Q.23.   In which part of the cell is DNA present/found? Where can the RNA be found in a cell?

Ans.      DNA is found in the nucleus of a ceil. The nucleic acid, RNA is found in the cytoplasm and nucleoplasm in the nucleus of a cell depending on whether the cell is prokaryotic or eukaryotic.

Q.24.   What is the need of extracting DNA?

Ans.     Extracted DNA can be analyzed further for better understanding of the genetic make up of an organism.

Q.25.   What is the difference between nucleoside and nucleotide?

Ans.      Nucleoside is made up of pentose sugar and nitrogenous base, while nucleotide is made up of pentose sugar, nitrogenous base and phosphoric acid.

Q.26.   What is the role of cellulase enzyme in extracting DNA?

Ans.     The enzyme cellulase helps in the digestion ofcellulosic cell wall of the plant cell.

Q.27.   Name the three major steps involved in DNA extraction.

Ans.     The three major steps involved in DNA extraction are:

(i) Homogenisation     (ii) Deproteinisation   (Hi) Spooling.

Q.28.   Why glass rod is used for spooling of DNA?

Ans.      DNA has negative charge and gets attracted to positive charge present in the silica of glass, therefore glass rod should be used for spooling.

Q.29.   What does the DNA look like on extraction?

Ans.     DNA appears as white precipitate of very fine threads on the glass rod or spool.

Q.30.   Why the ice-chilled condition should be preferred for isolating DNA?

Ans.     DNA begins to denaturation at room temperature by the action of DNA as present in cell extract, therefore whole procedure of DNA extraction should be carried out in ice-chilled condition.

Q.31.   Give the components of homogenisation media.

Ans.     Homogenisation media consists of

(i)      Sodium Dodecyl Sulphate (SDS)

(ii)     Ethylene Diamine Tetraacetic Acid (EDTA)

(iii)    (Hi) Sodium Chloride (NaCl) (non-iodised).

Q.32.   Why coldness is required during the conducting of experiment ?

Ans.     Using ice-cold water and ice-cold alcohol will increase your yield of  DNA. The cold water protects the DNA by slowing down enzymes that can break it apart. Why would a cell contain enzymes that destory DNA ? These enzymes are

Q.33.   Why the mixture should be allowed to stand for few minutes.

Ans.     If the cell and nuclear membranes are still intact, DNA will settle at bottom layer. Letting the test tube of mixture and alcohol sit for 30-60 minutes. More DNA precipitate into the alcohol layer over time.

Q.34.   Why salt should be added ?

Ans.     Salty water helps the DNA precipitate (solidify and appear) when alcohol is added.

Q.35.   Why detergent should be added to see DNA ?

Ans.      A cell’s DNA is usually protected from such enzymes (called DNases) by the nuclear membrane, but adding detergent destroys that membrane.

Q.36.   DNA precipitates in presence of alcohol. Is it still soluble in alcohol ?

Ans.     Yes.

Q.37.   What is the role of enzymes ?

Ans.     The two most common enzymes used in meat tenderizer are Bromelain and Papain. These two enzymes are extracted from pineapple and papaya, respectively. They are both proteases, meaning they break apart proteins. Enzymatic cleaning solutions for contact lenses also contain proteases to remove protein build-up. If you use pineapple juice or contact lens cleaning solution - just use a few drops.

Additional Resources / Sources :

Laboratory Manual Biology for class XII - Published by NCERT.

Significance & Overview Of Biology Class XII Practicals 

There are altogether twenty-five exercises in the present manual which are based on Biology curriculum for Class XII.

Practical - DNA Extraction ( OCR Gateway GCSE Biology )

Revision note.

Extraction of DNA from Fruit

Observing dna in the lab.

• This is not a core practical but still a worthwhile experiment
• The molecular appearance of DNA is very familiar, but can we actually extract this important molecule from cells and look at it?
• DNA can actually be extracted from fruit using some basic classroom equipment
• Strawberries, bananas and kiwis can be used
• The detergent breaks down the cell membranes (and the nuclear membranes ), causing the fruit cells to release their DNA
• The salt causes the DNA to stick together
• This removes any debris (big, insoluble bits of cell) from the mixture
• This causes the DNA to precipitate (i.e. to come out of solution ) as DNA is not soluble in cold alcohol
• The DNA will appear as a stringy white precipitate (a solid)
• If needed, this precipitate can be carefully extracted using a glass rod

A simple method for extracting DNA from fruit

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