DNA Extraction from Strawberry

DNA Lab objectives■ I will extract DNA from the fruits that we eat

such as strawberry by following DNA extraction protocol. (Steps)

■ I will explain the purpose of each step in the extraction procedure as it relates to the physical and biochemical characteristics of cells.

■ I will use standard safety practices for all classroom laboratory and field investigations.

■ I will use tools and instruments for observing, measuring, and manipulating scientific equipment and materials.

University of California Davis Partnership for Plant Genomics Education 2007

banana

onion

kiwi

Wheat germ

peas

strawberry

broccoli

Some questions to get you thinking about today’s lab:

One way to purify a molecule is to get rid of everything but that molecule. If we want to isolate DNA from strawberry, what do we have to get rid of?

What materials would you use to do that?

What can we do with the DNA once we’ve purified it?

Three Main Steps in DNA Extraction

■ Break the cells apart.

■ Release DNA from nucleus.

■ Precipitation of the DNA.

Protocol1. Get 2 pieces of strawberry and put them in a

zip lock bag.

2. Add 20 ml of extraction solution to the zip lock bag. Make sure the bag is closed without much extra air. Mush the strawberry thoroughly but carefully so the bag doesn't’t break, for about 5 minutes.

What does mushing the strawberry do?

3. What do you think the extraction solution is? What does it do to the strawberry?

5. Filter the mixture through the coffee filter.

What is being filtered out? What is going through the filter?

Put 2ml of the filtered juice in a tube.

7. Being careful not to shake the tube, add approximately 2-3 ml of cold isopropyl alcohol.

What do you think the alcohol does? Why do we want it cold?

8. Take a look at your tube. What do you see in the top, and lower portions of the liquid? Draw your observation.

9. Place a pipette into the tube and gently transport the DNA into the microtube. Be careful not to mix the alcohol and soapy layer.

Discussion Questions

■ Where can DNA be found in the cell?

■ What is DNA?

■ What are the three basic steps in any DNA extraction?

■ What is the purpose of the detergent? Of the sodium chloride? Of the alcohol?

■ Describe the appearance of your final product. Is this a pure DNA sample?

■ List some practical applications where extracting DNA is necessary.