DNA Extraction From Living Things
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:
Know how to extract DNA from living things
Understand DNA is in the food that they eat
Learn that DNA is found in all living things
Observe what DNA looks like
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) -
What do you think DNA looks like?
Where is DNA found?
Why do organisms have DNA?
Materials
Blender
Green Split Peas
1/8 teaspoon table salt
1 cup cold water
Cup
Strainer
Liquid detergent
Meat tenderizer
Rubbing alcohol
Test tube
Tooth pick
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?
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
2. What was the purpose of blending split peas?
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
3. Why does the detergent do to the soup?
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
4. Explain what happened when you added the alcohol in the last step?
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
5. Is there DNA in your food? How do you know?
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
Lab adapted from: http://learn.genetics.utah.edu/content/labs/extraction/howto/
New York State Science Standards-Core Curriculum Living Environment
Standard 1 Key Idea 2-Beyond the use of reasoning and consensus, scientific inquiry involves the testing of proposed explanations involving the use of conventional techniques and procedures and usually requiring considerable ingenuity.
Standard 4 2.1f-In all organisms, the coded instructions for specifying the characteristics of the organism are carried in DNA, a large molecule formed from subunits arranged in a sequence with bases of four kinds (represented by A, G, C, and T). The chemical and structural properties of DNA are the basis for how the genetic information that underlies heredity is both encoded in genes (as a string of molecular bases) and replicated by means of a template.
National Science Learning Standards
Content Standard C: As a result of activities in grades 9-12, all students should develop understanding of the molecular basis of heredity, and matter, energy, and organization in living systems
Content Standard E: As a result of activities in grades 9-12, all students should develop abilities of technological design and understandings about science and technology