Isolate DNA from fruit fly Drosophila melanogaster and understand the role
of DNA and proteins
1. Obtain fruit flies that are already placed in a centrifuge tube. Place the flies
2. One student should use the regular Squishing Buffer (SB+) and the other
should use Squishing buffer that does not contain either SDS/Proteinase K
3. Each student should grind the flies to increase the surface area and allow the
Squishing buffer to interact more.
4. A. Student should add SB+ (125 m) into tube and grind. Label tube.
B. Student should add SB- (125 m) into tube and grind. Label tube.
5. Put tubes in 60 C water bath (Optimal temperature of the enzyme proteinase
6. Centrifuge tubes for 3 mins at 14000 rpm. Balance the tubes by placing the
tubes in opposite sides.
7. Top part should look oily and is the supernatant. There should be debris at
the bottom. Using the P200 with the yellow tip transfer 200 m of the
supernatant (contains the DNA) into a new test tube.
8. Add 20 m of 5M NaCl into the tube.
9. Add 436 m of ethanol, leave test tube in ice for 5 mins.
10.Centrifuge the tubes for 5 mins at 14000 rpm. Remove the ethanol by
pouring in into a liquid waste bucket
11.Add 500 l of 70% ethanol to wash pellet. Centrifuge the tube for 5 mins at
12.Pour out ethanol and blot pellet
13.Add 50 l of TE to the tube and gently pipette the liquid up and d