DNA Extraction and Beaded Bracelets

Activity Language
Time Needed for Activity
Students are introduced to DNA, base pairs and genes and learn the anatomy of DNA by building a DNA beaded bracelet and extracting DNA from bananas.

This activity will explore deoxyribonucleic acid (DNA), the base pairs that make up DNA and how this creates genes. Students will learn about differences in plant and animal cells, and how the features of these cells can be altered to extract DNA. Students will then learn the anatomy of DNA by building a DNA beaded bracelet and extracting DNA from bananas.

What You Need

For the DNA bracelet activity, each student will need:

  • 1 butterfly DNA sequence
  • 2 10-inch long pieces of stretchy cord
  • Beads: 13 red, 13 green, 8 blue, 8 yellow

All materials should be placed in an envelope, taped closed and handed to the students.

For the Banana DNA extraction, each pair of students will need:

  • 1 inch piece of banana
  • 1 small Ziploc baggie
  • Pinch of salt
  • 1 medium-sized plastic cup
  • 1 basket type coffee filter
  • 1 elastic band
  • 10 mL of at least 95% rubbing alcohol (2 full bottle for a class of approximately 20 students)
  • 5 drops of dish soap
  • Stir stick

Lesson Plan:

Link to PowerPoint file: 

DNA presentation Grade 8 virtual

 

Safety Notes

Ensure you are familiar with Let's Talk Science's precautions with respect to safe delivery of virtual outreach to youth. These precautions can be found in the manual for this activity. 

Activity Specific Safety: advise students to not eat or drink while doing the extraction lab, including not eating or drinking the rubbing alcohol, soap, salt, or the banana. Ensure that the students have no allergies to the materials being used before conducting this activity. 

What To Do

DNA Bracelet:

We'll start with this strand and then you will build the complimentary strand. 

Have the educator hand out the envelopes containing the materials for their bracelet.

  1. Instruct students to remove the paper and the 2 elastic strands. Tie a knot at one end of both strands and then tie them together. 
  2. Using only one strand, put a green bead on, then red, yellow, green, etc. following the order of the small piece of butterfly DNA sequence. 
  3. Once you have finished adding your beads, tie a knot and start building the complementary strand remembering that you pair A (adenine) with T (thymine) and C (cytosine) with G (guanine) and match the colours. 
  4. Once you are done creating the strands, twist them like a helix, tie them together and wear them as a bracelet.

Banana DNA Extraction: Ensure to discuss how each step of the recipe relates to getting the DNA out of a plant cell.

  1. Have the teacher distribute a baggie and a 1-inch long piece of banana. Have them squish the banana in the baggie without breaking the baggie. This represents breaking the cell wall of the plant cell. 
  2. While the students are squishing the banana, have the educator pour about an inch of water into the plastic cups. Get the students to add this water to their baggie (The educator can go around and directly add the water to the bag if this is easier). Have the students continue to squish the banana in water. 
  3. The teacher can then add a pinch of salt into each of the baggies. Be sure that the baggie is closed tightly before squishing more. They should squish for about 5 minutes in total. 
  4. Have the teacher hand out coffee filters, elastics, stir stick and the plastic cup. Show them how to put the coffee filter on the cup so there is little room for liquid to sit in and secure the coffee filter with the elastic band. 
  5. Add the banana mush to the filter a little at a time so it doesn't overflow and let it filter through. 
  6. Once the filtrate has passed through the coffee filter and into the cup, show the students how to remove the coffee filter without losing its contents into the cup. Place the coffee filter into the plastic baggie.
  7. Ask the educator to place a small squirt of dish soap into the cup with the filtrate inside. Ask the students to stir gently for 1-2 minutes as we don't want bubbles to form.
  8. Have the educator bring around the rubbing alcohol. Have the students tilt their cup to the side and pour slowly so the rubbing alcohol runs down the cup to form a layer on top of the filtrate. It must be done slowly and on an angle in order to achieve this filtrate.
  9. Let the cup sit for a moment and students will see a white precipitate forming. This precipitate is the Banana's DNA. They can pick it up with the stir stick.

Discovery

What's Happening?

In the banana DNA extraction, we are using a specific recipe to allow us to extract the DNA from a plant cell. The DNA is found in the nucleus of the plant cell and there is a specific pathway through the cell to get there. In order to get to the nucleus, we must break down the cell wall. The cell wall is what gives the plant structure and helps the cell hold its shape. By squishing the banana in the plastic baggie, we have broken down the cell wall. 

Next in our pathway to the nucleus is the cell membrane. The cell membrane is made up of a lipid bilayer (basically a layer of fat) which allows things to move in and out of the cell. We used the dish soap to help break up the fatty layer and we were able to break through the lipid bilayer. 

The process of squishing and adding soap gives us our DNA. DNA is a charged molecule, so we must remove this charge to make our DNA less soluble in water to help us see our DNA. Adding the salt to the squished banana neutralizes the DNA and removes the charge. 

The last part of our recipe is the rubbing alcohol. The rubbing alcohol will cause the DNA to form a solid that we are able to see and pick up with our stir sticks. 

What's Happening?

In the banana DNA extraction, we are using a specific recipe to allow us to extract the DNA from a plant cell. The DNA is found in the nucleus of the plant cell and there is a specific pathway through the cell to get there. In order to get to the nucleus, we must break down the cell wall. The cell wall is what gives the plant structure and helps the cell hold its shape. By squishing the banana in the plastic baggie, we have broken down the cell wall. 

Next in our pathway to the nucleus is the cell membrane. The cell membrane is made up of a lipid bilayer (basically a layer of fat) which allows things to move in and out of the cell. We used the dish soap to help break up the fatty layer and we were able to break through the lipid bilayer. 

The process of squishing and adding soap gives us our DNA. DNA is a charged molecule, so we must remove this charge to make our DNA less soluble in water to help us see our DNA. Adding the salt to the squished banana neutralizes the DNA and removes the charge. 

The last part of our recipe is the rubbing alcohol. The rubbing alcohol will cause the DNA to form a solid that we are able to see and pick up with our stir sticks. 

Investigate Further

If the students are intrigued with DNA and genetics, they may be interested in learning how DNA plays a role in finding cures for cancer and other genetic diseases, making genetically modified organisms and foods, drug discoveries, etc. 

Investigate Further

If the students are intrigued with DNA and genetics, they may be interested in learning how DNA plays a role in finding cures for cancer and other genetic diseases, making genetically modified organisms and foods, drug discoveries, etc. 

Resources

Lesson Plan:

Link to PowerPoint file: 

DNA presentation Grade 8 virtual

Resources

Lesson Plan:

Link to PowerPoint file: 

DNA presentation Grade 8 virtual

Check out additional resources (articles, career profiles and more) on these topics from Let’s Talk Science: