DNA Extraction From Living Things

Jacqulyn Bodenmiller

Harlem Renaissance High School, Manhattan

Summer Research Program for Science Teachers

August 2009

 

 

Grade Level

9th & 10th Grade Living Environment (Biology)

Aim

How to extract DNA from anything living.

Expected Time

Teachers Prep: 10-20 minutes

One class period (50-60 minutes)

Performance Objectives - Students Will Be Able To:

Purpose - The purpose of this lab is to extract DNA from split peas so that it can be seen by the naked eye.  This will also show that DNA can be extracted from anything living.

Do Now (Pre-lab questions) -

  1. What do you think DNA looks like?

  2. Where is DNA found?

  3. Why do organisms have DNA?

Materials

Procedure

First, you need to find something that contains DNA. Since DNA is the blueprint for life, everything living contains DNA.

For this experiment, we like to use green split peas. But there are lots of other DNA sources too, such as:

Step 1:  Blender Insanity!!!

Put in a blender:

Blend on high for 15 seconds.

The blender separates the pea cells from each other, so you now have a really thin pea-cell soup.

Step 2- Soapy Peas

Pour your thin pea-cell soup through a strainer into another container (like a measuring cup).

Add 2 tablespoons liquid detergent (about 30ml) and swirl to mix.

Let the mixture sit for 5-10 minutes.

Pour the mixture into test tubes or other small glass containers, each about 1/3 full.

Step 3- Enzyme Power

Add a pinch of enzymes to each test tube and stir gently. Be careful! If you stir too hard, you'll break up the DNA, making it harder to see.

Use meat tenderizer for enzymes. If you can't find tenderizer, try using pineapple juice or contact lens cleaning solution.

Step 4- Alcohol Separation

Tilt your test tube and slowly pour rubbing alcohol (70-95% isopropyl or ethyl alcohol) into the tube down the side so that it forms a layer on top of the pea mixture. Pour until you have about the same amount of alcohol in the tube as pea mixture.

Alcohol is less dense than water, so it floats on top. Look for clumps of white stringy stuff where the water and alcohol layers meet.

Conclusion and analysis questions

1.       What did DNA look like?  Is this what you expected?

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2.       What was the purpose of blending split peas?

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3.       Why does the detergent do to the soup?

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4.       Explain what happened when you added the alcohol in the last step?

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5.       Is there DNA in your food?  How do you know?

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Lab adapted from: http://learn.genetics.utah.edu/content/labs/extraction/howto/

 

New York State Science Standards-Core Curriculum Living Environment

 

National Science Learning Standards