Extracting DNA from a Banana
Extracting DNA from a banana? Yes, that’s what we’re going to do today!
Let’s first cover some genetics information shared with us by Lindsay Zetzsche, who is the owner of Science Geek Games and a genetic counselor. She has a passion for making genetics and biology knowledge accessible for students ages 8 and up.
Genetics is a fascinating field of science. It is the study of genes, which are present in all living things, from humans to worms, to bananas, and even giant redwood trees. Genes are the instructions for living things, for how to grow and how to function. Each gene is an instruction code, like a recipe. Humans have over 20,000 genes, and while we know a lot about many genes, scientists are still figuring out what many of them do!
We inherit our genes from our parents and pass them on to our children. Genes code for traits like eye color, hair color, and height, and they also code for proteins like enzymes that help us use energy in our body. Genes are made of Deoxyribonucleic Acid (DNA), and it is amazing that the four DNA bases – adenine (A), cytosine (C), guanine (G), and thymine (T) – make up the genetic language that writes all of our genes. Even more amazing is that humans share 99.9% of the same DNA; that 0.1% difference between us is what makes us all so unique and interesting!
Genetics plays a role in tracing ancestry and can also be used to solve crimes – DNA samples can be obtained from even the most minute strands of hair (if the follicle is still intact) or saliva from a person’s cup.
Genes are very important in the practice of medicine as well. Many people have genetic conditions caused by a change in a gene that leads to specific health issues. Most genetic conditions are rare, but collectively, they are very common.
Knowing about genetic conditions is helpful because sometimes there are treatments. Even cancer treatments can sometimes be guided by knowing more about the genetic changes found in a cancer tumor. There are a lot of interesting careers focused on genetics, including genetic variant analyst, genetic researcher, forensic scientist, genetic counselor, and medical geneticist.
Genes are composed of DNA and are grouped together on structures called chromosomes. Humans usually have 23 pairs of chromosomes (46 chromosomes). The chromosomes are located in the nucleus of cells.
When scientists want to extract DNA from cells, they must follow several steps to break open the cells and release the chromosomes and DNA from the nucleus. They use a solution that helps the DNA come together and then precipitate out of the solution. A precipitate is when something in a liquid changes to a solid. Adding an alcohol like isopropyl alcohol can help DNA precipitate. Extracted DNA looks like a clump of white strands.
After you have finished extracting DNA from a banana, reinforce what you have learned with the DNA card game, Variation. (aff link) Learn more about the game in our review.
Extracting DNA from a Banana
DNA is in all living things, including plants and fruit! The genetics activity involves extracting DNA from a banana.
Don’t forget! There is a printable lesson with a lot more information on DNA, pages that accompany this activity, and other activity pages. See the request form near the end of this post.
Notes before starting:
- Request the free worksheet download before starting.
- Place the 91% rubbing alcohol in the freezer at least 2 hours before starting this activity.
- Use distilled water.
- Use clear liquid dish soap or hand soap. Check for EDTA on the label.
Extracting DNA from a Banana: Materials Needed
- A banana
- Distilled water
- Clear plastic zip bag
- Clear liquid dish soap, hand soap, or shampoo (should have EDTA in it)
- 2 clear cups
- Table salt
- Spoon for stirring
- Coffee filter
- Measuring spoons (tablespoon, teaspoon, and ¼ teaspoon)
- Isopropyl alcohol (91% or higher) – put in freezer for at least 2 hours in advance
- Wooden stirring stick or toothpick
Extracting DNA from a Banana
Instructions
- Add a 1-inch section of banana to the plastic zip bag, seal it.
- Mash it up! You don’t want solid chunks. Then add 1 tablespoon of water and mash some more.
- It should be nice and liquid-y.
- In one of the cups, add 1 teaspoon of clear soap, ¼ teaspoon of salt, and 2 tablespoons of water. Stir gently until the salt has dissolved; try to avoid creating bubbles or foam.
- Add the banana mixture to the cup with the soap mixture and stir gently.
- Put a coffee filter over the 2nd cup so that there is at least 1” of space from the bottom of the cup. You can tape it or use a rubber band if you want it more secure.
- Pour the banana mixture onto the filter while holding the filterin place. Let the mixture drip into the cup; wait about 10 minutes.
- Discard the filter and the remaining banana mixture that did not filter into the cup.
- Get cold isopropyl alcohol and measure out 1 tablespoon. Slowly dribble the alcohol down the side of the cup with the filtered banana mixture. You can use a dropper or spoon to add the liquid slowly. Let this sit for 4 minutes.
- Observe the mixture. What do you see?
- Slowly stir the mixture with the wooden stirring stick. Ifyou notice some white strands attached, this is the DNA. You can swirl themlike a strand of spaghetti.
- You have extracted DNA!
Video
Just like humans, plants like trees and fruit have DNA and genes to help them grow and have different traits. Some bananas have 11 pairs of chromosomes, so 22 chromosomes total. Most of the bananas we eat have 3 copies of each chromosome, meaning 3 copies of each gene and 33 total chromosomes.
More DNA Activities
Another activity to learn about DNA is to play the DNA matching card game (affiliate link) called Variation. This game offers multiple ways to play, allowing you to learn about DNA base matching and creating DNA sequences. It is designed for play with a friend or family member. It also has different genetic facts on several of the cards. Challenge: create your own variation on how to play!
Extracting DNA from a Banana – Worksheet Printable
Input your email address below and request the 30+ page lesson on DNA, with instructions and worksheets for the DNA extraction activity. You will be added to our email community and can unsubscribe at any time. Thank you!
Other DNA and Genetics Resources
Educational resources from the National Human Genome Research Institute
Science Geek Games DNA matching game
Lindsay Zetzsche is a proud science geek and licensed genetic counselor with formal business education and genetics experience in the clinical, laboratory, and insurance settings. Her most recent position was Director of Genetics Operations at a large national insurance company. Lindsay is the Owner & Founder of Science Geek Games, developing science-based games to ignite a spark of curiosity and joy of learning about the fascinating world of biological sciences through the power of play. She lives in Rochester, MN with her husband, 2 kids and a menagerie of pets. Lindsay enjoys spending time with family, reading, and speed puzzling in her free time.