Fruity DNA Lab InstructionsName ______

Ramshaw – BiologyHour ______Date ______

Objectives:

  • Separate and collect the DNA from fruit cells
  • Describe the appearance of DNA extracted from a cell
  • Relate the location of DNA in a cell to procedures for extracting it

Materials:

  • Goggles
  • Banana or Strawberry
  • Mortar and pestle
  • Salt
  • Dawn soap
  • Coffee filters
  • Funnel
  • Test tube
  • Test tube rack
  • Paper towel
  • Ethanol
  • Inoculating loop
  • Small beaker
  • Water

Purpose:

DNA is often extracted from cells and purified so scientists can study it. The DNA that is extracted can be called a “DNA fingerprint” for that organism. You will be using a banana or strawberry to practice this technique, but it can be done on any living cell, plant or animal. Once scientists know the DNA fingerprint of an organism, they can study the DNA sequence for a variety of reasons. Some of these reasons may be to solve a crime where cells have been left behind, determine family relationships, alter current sequences to make genetically engineered foods and medicines, or even to determine if you have inherited a genetic disorder.

Overview:

The process of extracting DNA, regardless of its original source, involves the following steps. The first step in extracting DNA from a cell is to lyse, or break open, the cell. One common way to lyse cells is to grind a piece of tissue along with a mild abrasive material in a mortar with a pestle. After the cells have been broken open, a solution containing salt and a detergent containing the compound SDS, or sodiumdodecyl sulfate, is used to break down and emulsify the fat and proteins that make up the cell membrane. Finally, ethanol is added. Because DNA is soluble in water, the addition of ethanol causes the DNA to precipitate, or settle out of solution, leaving behind all remaining cellular components that are not soluble in ethanol. Finally, the DNA can be spooled, or wound onto an inoculating loop, and pulled from the test tube.

Procedure:

  1. Put on safety goggles. Make sure hair, clothing, and jewelry are appropriate for the lab setting. Cover your toes!
  2. Place a piece of banana or strawberry in a mortar. Add a small amount of salt.
  3. Pour a short squeeze (~10 drops) of Dawn soap into the mortar.
  4. Use a pestle to grind the ingredients until they form a fluid. No chunks should be visible and it should be semi-runny, but be careful not to not over-grind.
  5. When the mixture is somewhat smooth, add 10 to 20 mL of tap water to your mortar and mix well. This will help you pour it out easier (next step).
  6. Place a coffee filter into a funnel (fold it as Ms. R instructs you to). Pour the contents of the mortar through the coffee filter into a test tube until it contains at least ¼ to ½ an inch of solution in the bottom of the test tube. Call for Ms. Ramshaw if you have trouble with this step.
  7. Slowly pour a small amount of cold ethanol into the tube at a 45 degree angle. (Call Ms. Ramshaw over when you are at this step, she will do this step for you.)
  8. Observe the interface line, the place where the ethanol meets the solution you put in the test tube. You should see a cloudy clump of material forming. This is the DNA! Record observations about what it looks like in the test tube.
  9. Gently insert an inoculating loop into the test tube as far as the interface line. Carefully and slowly, move the loop in circles, being careful not to shake the tube. This is called “spooling”.
  10. Lift out the DNA when it attaches to your loop. Try to removethe entire DNA “clump” at one time. Place what you have collected on a paper towel and make observations. It is ok to touch the DNA if it will help with your observations.
  11. To clean up, turn the water on in the sink and let it run. Empty the contents of your test tube down the sink. Clean and dry your test tube and put it back in the rack. Throw the coffee filter in the trash. Throw the DNA in the trash. Return all materials back to their original location (including your goggles). Clean up your lab area. Wash your hands when you are finished.Follow all other clean up procedures given by Ms. Ramshaw.

Answer the conclusion questions as a group and turn into the tray on my desk when you are finished.

Fruity DNA Lab Conclusion QuestionsRamshaw - Biology

All students in your group must participate in the completion of this worksheet. All questions must be completed, even if you have less than 4 in your group.

Student #1: Name ______

  1. Describe the appearance of the DNA you spooled from the crushed banana cells.

In the tube:

Out of the tube:

  1. What was the purpose of adding salt to the fruit in the mortar? (read page 1)

Student #2: Name ______

  1. What happens to the cell when Dawn is added to the fruit mixture in the mortar? (read page 1)
  1. What was the purpose of filtering the fruit mixture through the coffee filter? (read page 1)

Student #3: Name ______

  1. What was done to the DNA so that it could be observed and spooled? (read page 1)
  1. How can you determine whether the material pulled from the test tube was DNA? (read page 1)

Student #4: Name ______

  1. Which 2 barriers protect and keep the DNA in the cell? ______and the ______. Describe what you did to break those 2 barriers (so the DNA could be extracted):
  1. Why would scientists find this technique (being able to extract DNA from a living thing)to be helpful in real life? (read page 1)