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Marketplace DNA Extraction

Materials

• Fresh vegetable or fruit
• Table salt
• Meat tenderizer
• Water
• Liquid dishwashing detergent
• Rubbing alcohol (70 to 95% isopropyl alcohol)
• 6 Test tubes
• 2-cup glass or plastic container
• Wooden skewer
• Small strainer
• Blender
  

Tiime Requirements

• 45-60 Minutes

Purpose

The purpose of this activity is to confirm with your young scientists the presence of DNA in all living cells and to teach basic biology laboratory skills.

This activity will extend your students' understanding of the cellular location of DNA. It will also give them a foundation in laboratory work. Also, this experiment may help your students recognize the chemical function of many household products.

The Science Behind Marketplace DNA Extraction

This procedure for extracting DNA from marketplace produce is designed to use common products that students may encounter in other laboratory experiences and often in their daily lives.

This procedure is founded on the fact that all living things have DNA. DNA can be isolated through a series of simple steps.

Cell Separation: Table Salt
By blending the produce sample and table salt, your students will be breaking the plants' cell walls and separating the cells. This is due to both the physical process of aggressively agitating the cells in the blender and the chemical process of adding salt to the solution. The salt causes the precipitation of proteins and carbohydrates located in the produce, further helping to separate the cells.

Cell and Nuclear Membrane Destruction: Detergent
The cell membrane is composed of lipids (fats) and proteins. The detergent acts on these lipids like it does with other fats (think of how detergent works with grease on dirty dishes) and captures the lipids and proteins. In the process of capturing these molecules, the cell membrane is lysed (or broken), destroying the membrane and releasing the parts of the cell into the solution.

DNA Unwind: Meat Tenderizer
Meat tenderizer acts as an enzyme when interacting with the solution. DNA, which is usually contained in the cell as long strands wrapped around proteins, needs to be unwound in order to be completely separated from the proteins and other cell contents. The meat tenderizer acts like an enzyme in that it cuts out the proteins from the DNA-protein complex.

Separation of DNA from Solution: Rubbing Alcohol
At this point of the procedure, the DNA has been released from the cell and freed from the proteins it usually accompanies, but it is mixed in with all of the other cell components in the solution. To separate and isolate the DNA from all of the other cell "junk," you can add rubbing alcohol to the solution that forms a layer on top of the solution. This addition will cause the DNA to precipitate and rise up into the alcohol layer.

How to Store DNA
Your students can extract their DNA with a wooden skewer and place it in a small, sealable container holding alcohol. As long as the container is tightly sealed and is not shaken much, the DNA should remain. However, there is a chance that the DNA could continue to degrade if any enzyme is transferred with the DNA into the new container.

For more information on science behind this procedure, visit http://learn.genetics.utah.edu/units/activities/extraction/faq.cfm.

Educational Objectives

The National Academic Press published the National Science Education Standards. The following grade level goals reflect the level of understanding students should have in genetics, inheritance, and DNA structure and function.