COFFEE BREAK
VI.) Touching DNA: Strawberry
DNA Extraction
DNA Isolation using
Strawberries
(wear eye protection, or be
careful).
Working in groups, 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