Strawberry DNA Extraction
DNA Isolation using Strawberries (wear eye protection, or be careful).
Working in groups (for supervision), but each individual will do their own.
- Place 1 strawberry in the plastic bag. Remove air and seal.
- Mash strawberry for 2 minutes.
- Add ~10 ml DNA Extraction buffer (Pre-measured). Remove air and seal.
- Mash for 1 minute.
- Pour solution through coffee filter into paper cup
- Pour ~2 ml of this solution back into the 15 ml tube. It will be very red.
- Pour ~ 4 ml (2X the volume of strawberry solution) of cold ethanol (found on freeze door in 50 ml tubes) so that it lays on top of the strawberry solution. (NOTE: can use 1X volume of room temperature isopropanol, rubbing alcohol, as a substitute)
- If the tube just sits, there will be DNA at the interface with bubbles in it. If you gently rock the tube, more will come out of solution and eventually float to the top. (NOTE: if the DNA doesn’t come out of solution at home, add a little more salt)
Extraction buffer:
100 ml shampoo without conditioner or dishwashing liquid
900 ml distilled water
15 grams NaCl
Supplies:
Frozen Strawberries: allow to come to room temperature, or at least un-freeze.
Sandwich bags (good ones with good zip-locks)
Cheese cloth or coffee filter
Funnel or aluminum foil (to make a funnel)
Cups, or flask, 15ml centrifuge tubes
Why’s:
Strawberries? 8 times the amount of DNA of normal cells
Why frozen? Ice disrupts cells. Can use fresh strawberries, too. Cheap!
Detergent? To disrupt cell membranes to liberate the DNA
Salt? To shield the negative charges on DNA to allow precipitation
Alcohol? To cause DNA to precipitate
Great recipe for basic
DNA extraction in Grade 7 Biology
DNA extraction
The idea of using strawberry for this activity is more preferable than the one I did with my students in the last school year in the sense that rather than using strawberry, banana etc. each student had to come up with their spit sample!!!.
You can imagine how much classroom management strategies that will be required to ensure sanity in this lab.
In addition, all the materials we used today are available in my school because my principal is really interested in getting the science department off her feet this coming school year.
I'm definitely going to use this method when we get to genetics and introduction to DNA structure.
Inquiry lessons- DNA of Strawberries
The inquiry lesson done this AM with strawberries is something I can do in my 4th grade class. One feature of this lesson that stands out is the direction sheet which gives very clear directions on what to do, how and when to do it. My students will be able to follow the directions if they are clearly writen like these.
The other thing is the idea of working in groups though individually. That will make everyone able to do something, and at the same time get as much help as possible from others in the group.
I discovered that there could be variations to what we did. If more alocohol was poured what would be the effect? What does the DNA feel like? How about putting water to dilute the alcohol content? These are all areas of variations that could be added to the activity. In the course of finding answers to these questions, students will themselves be ivolving different fields or disciplines such as writing.
Though DNA may not be part of our curriculum in 4th grade, I can always adapt other lessons to follow this format. Good engaging and interesting lesson.
Strawberries
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