SBI4U: Molecular Genetics
Name: _______________________
Date:_____________
DNA EXTRACTION LAB
(Adapted from pages 192-193, Biology 11, McGraw-Hill Ryerson, 2001)
Purpose: to extract DNA from banana tissue
Materials:
250mL beaker
50 mL beakers (2)
glass stirring rod
graduated cylinder
pestle and mortar
cheesecloth or paper towel
small piece of banana tissue (approximately 1cm3)
0.9% NaCl (0.9g of NaCl in 100mL distilled water)
10% dishwashing detergent (10mL in 90mL water)
95% ethanol (ice cold)
Procedure:
1. Place the sample of banana in the mortar.
2. Add 10 mL of 09% NaCl solution and grind thoroughly with the pestle for 2 to 5 minutes.
3. Strain the solution through three layers of cheesecloth or paper towel and collect the liquid in
the 250 mL beaker.
4. Pour the liquid into one 50 mL beaker and add 1.5 mL of 10% dishwashing detergent.
5. Estimate the volume of the extract in the beaker. Then measure approximately twice as much
ice-cold 95% ethanol into the other 50 mL beaker.
6. Slightly tilt the beaker holding the banana extract and gently add the ethanol to the suspension
by pouring ethanol down the inside of the beaker.
7. Use the glass stirring rod to gently stir the mixture. When you see a precipitate form at the
boundary of the two liquids, twirl the rod to spool the DNA sample onto the glass rod.
Questions: (2 marks each)
1. Describe the appearance of the DNA you extracted.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
2. List the 3 main components of DNA.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
3. Could you observe these components? Why or Why not?
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
4. Draw a labelled diagram of a DNA molecule.
5. What did the addition of dish detergent do to the banana cells?
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
6. Would you use the same procedure to isolate mitochondria from the cell? Why or why not?
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
7. List 2 types of careers require isolating DNA?
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
8. Quality/Amount of DNA extracted _____ / 1
/15
_____