Yummy!

• The long, thick fibers of DNA store the information for the functioning of the chemistry of life. DNA is in every cell of plants and animals. The DNA found in strawberry cells can be extracted using common, everyday materials. We will use an extraction buffer containing salt, to break up protein chains that bind around the nucleic acids, and dish soap to dissolve the lipid (fat) part of the strawberry cell wall and nuclear membrane. This extraction buffer will help provide us access to the DNA inside the cell.

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Do strawberries contain DNA?

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If I test strawberries for DNA then I will find that strawberries do contain DNA because all living things have DNA.

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3-4 Strawberries

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DNA Extraction Buffer

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Plastic Baggie

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250 ml beaker

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Filter

• • • • • Rubber band Alcohol Test tube Glass rod Microfuge tube

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Place1-2 strawberries in a Ziploc bag.

Smash/grind up the strawberry using your fist and fingers for 2 minutes. Careful not to break the bag!! Add 10 mL of DNA Extraction buffer (salt and soap solution) to the bag.

Kneed/mush the strawberry in the bag again for 1 minute. Prevent getting too many bubbles!! Assemble your filtration apparatus as shown by the teacher.

Pour the strawberry slurry into the filtration apparatus and let it drop directly into your test tube.

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What do you think the DNA will look like?

Where is DNA found?

What is the purpose of the initial smashing and grinding of the strawberry?

What is the purpose of the salt?

What is the purpose of the soap?

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What is the purpose of filtering the strawberry slurry?

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Transfer the filtrate into the test tube.

Hold the tube at an angle while the teachers slowly adds cold ethanol. OBSERVE  Dip the glass rod into the tube where the strawberry extract and ethanol layers come into contact with each other. Carefully wrap the DNA around the glass rod.

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Have the teacher pour some ethanol into the microfuge tube.

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Carefully transfer your DNA into the microfuge tube. 

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What was the purpose of adding ethanol to the filtered extract?

What did the DNA look like? Relate what you know about the chemical structure of DNA to what you observed today.

Explain what happened in the final step when you added ethanol to your strawberry extract. (HINT: DNA is soluble in water, but not in ethanol.

A person cannot see a single cotton thread 100 feet away, but if you wind thousands of threads together into a rope, it would be visible much farther away. Explain how this statement is analogous to our DNA extraction.

Why is it important for a scientist to be able to remove DNA from an organism? List two reasons.

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