Life Sciences Term 1

Aim: to enable participants to extract DNA from a given fruit

In your groups, collect the following materials:

• Strawberries
  
• Zip-closure sandwich bags
  
• DNA extracting solution (mix 1 cup dishwashing liquid detergent and 1/4 cup salt into 41/2 litres of water)
  
• Plastic cups
  
• Gauze or cheesecloth
  
• Rubber bands
  
• Test tubes
  
• Droppers
  
• Ice cold ethanol (place test tube of ethanol in a beaker containing ice cubes)
  

Procedure

• Place a strawberry in a zip-closure bag and remove most of the air before you seal the bag
• Mash the strawberry through the bag in your hand. Do not hit it against the table
• Add 2 TB of the DNA extracting solution
• Continue mixing and mashing the bag in your hand
• Place a piece of gauze over the opening of the cup and secure with a rubber band
• Carefully pour the strawberry mixture into the cup making sure to catch the solids with the gauze
• Take a dropper full of the liquid in the cup and place it in the test tube
• Add a dropper full of methylated spirits in the test tube
• Do NOT tilt or tip the test tube, DO NOT mix the two liquids
• Observe the line between the strawberry mixture and the ice cold ethanol
• You will note a white thread-like cloud appearing at this line
• This is strawberry DNA. The DNA will clump together and float to the top of the alcohol layer.

In your groups, discuss the following:

• Why was dishwashing liquid used?
• Why was salt used?
• What does the alcohol contribute to the experiment?

Record your thoughts below: each participant should post at least two comments and two replies.