Activity
DNA Extraction: A Berry Good Lab
This hands-on science lab is designed to teach students who are blind or who have low vision about DNA.
Background:
DNA, or Deoxyribonucleic Acid, is a special 5-carbon protein, consisting of a double helix. It looks like a ladder with the top and bottom of the ladder twisted. DNA is the blueprint (template) for taking amino acids and sequencing them to make proteins.
Materials
- DNA extraction buffer (water, dishwashing detergent, salt)
- funnel strawberries
- cheesecloth
- 50 mL test tube
- ring and ring stand
- stirring rod
- ethanol (ice cold)
- beaker
- Ziploc bag
Preparation
Teacher’s Notes
DNA Extraction Buffer
- Add 50 mL Palmolive Dishwasher detergent to a 1 L beaker
- Add 15 grams (2 teaspoons) of Sodium Chloride
- Fill with water to one liter
NOTE: It is critical to place the alcohol in a refrigerator overnight to achieve the best results.
- Place two strawberries in a Ziploc bag.
- Squish (ooh) the strawberries, using your fist and fingers for two minutes (very important for breaking open the cells).
- Add 20 mL of the DNA extraction buffer to the bag.
- Squish (ooh, again) the strawberries in the bag again for one minute, (very important to break up the proteins and dissolved the cell membranes).
- Set up your ring and ring stand. Place a funnel in the ring and put the beaker under the funnel. Place the test tube in the beaker.
- Place a square of cheesecloth into the funnel.
- Pour (not drink) the strawberry mixture into the cheesecloth and let it drip directly into your test tube (to separate out the components of the cell).
- After all the liquid has dripped into the test tube, slowly pour 40 mL of the cold ethanol into the test tube. Observe. This precipitates the DNA from the solution.
- Dip the stirring rod into the test tube where the strawberry liquid and ethanol layers meet. Observe what happens.
Questions:
- What is the scientific name for DNA?
- Describe what DNA is.
- What do you think is the purpose of the DNA extraction buffer; that is, what does the buffer do to the strawberry cells?
- Why do you think we used cold ethanol?
- Is it possible to extract the DNA from all plants and animals? Explain your answer.
Bonus:
Repeat this experiment and extract DNA from any living material of your choice. This is worth 15 points if you are successful in doing this and 20 points if you write a one-page report and include a lab journal.
NGSS Standards:
Middle School
- MS-LS1-1: Conduct an investigation to provide evidence that living things are made of cells; either one cell or many different numbers and types of cells.
- MS-LS1-2: Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.
High School
- HS-LS1-1: Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.
- HS-LS1-2: Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.
- HS-LS1-3: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.
By aroth
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