Science 10 with CSS teacher

Kitchen Lab—DNA Extraction

Instructions

To get started, you will need a source of DNA. The following instructions require you to use split peas as your DNA source.

You will need:

• 125 ml (1/2 cup) dried split peas

• .5 ml (1/8 teaspoon) salt

• 250 ml (1 cup) of ice-cold water

• A blender

• A strainer

• A container (bowl, plastic reusable container, or similar container)

• Liquid detergent (for example dish detergent)

• 3 ml (3/4 teaspoon) pineapple juice *

• Rubbing alcohol (chilled)

• A few toothpicks

• 3 small glasses OR 3 test tubes if you have them

*If you don't have pineapple juice, you can use contact lens cleaning solution or even meat tenderizer. This ingredient acts as an enzyme, which you will learn more about in the next lesson.

Procedure:

1. Combine dried split peas, salt and ice-cold water.

2. Mix in a blender on high speed for 15 seconds.

3. Pour the pea mixture through a strainer into another container.

4. Add about 30 ml (2 tablespoons) of liquid detergent to the mixture. Let it sit for 5 to 10 minutes.

5. Pour the mixture into the glass (or test tube) so that it is one-third full.

6. Then add 1 ml (1/4 tsp) pineapple juice to the glass container and stir gently.

7. Tilt the container and slowly pour chilled rubbing alcohol down the inside wall of the tube so that it forms a layer on top of the mixture. Keep pouring in alcohol until the tube contains about the same amount of alcohol as it does pea mixture.

8. In a few minutes, the DNA will rise into the alcohol layer from the pea mixture layer. You can use a toothpick to pull the DNA out.

Congratulations—you've just extracted the “master set of instructions” for split peas!

If your lab is not working the way you think it should be, check out these FAQs for some helpful hints by clicking here

Reflect on the 'Kitchen Lab' you have just completed by answering the following questions:

1. A student performs this activity, but does not manage to extract DNA from the sample. What are some things that they may have done wrong?

   Solution? click here

   There are many possible sources of error in this experiment. You might have come up with a possible error that is not on this list. Some that you may have thought of include:

   • using water that is not cold enough
   • not letting the final mixture sit for long enough
   • using the wrong strength of rubbing alcohol
   • not blending the original mixture for long enough
   • incorrect ingredient measurement
   • omitting an ingredient, for example salt, from the original mixture

2. What are some changes you could make to the procedure in order to determine more about DNA extraction?

   Solution? click here

   This experiment could be changed in many different ways, and the changes you suggest might affect the outcome of the experiment. Some possible changes include:

   • using different sources of DNA
   • using warm or hot water instead of cold water
   • omitting the salt to see whether DNA would still be extractable
   • blending different samples for different amounts of time
   • adding different enzymes to different samples
   • adding different concentrations of rubbing alcohol
   • letting different samples of the final mixture sit for different amounts of time