BIO 111: DNA Extraction: Strawberry DNA Spooling Background: The long, thick fib

Question

BIO 111: DNA Extraction: Strawberry

DNA Spooling

Background: The long, thick fibers of DNA store the information for the functioning of the chemistry of life. DNA is present 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 cells.

Pre-lab questions:

What do you think the DNA will look like?

Where is DNA found?

Materials:

Heavy duty ziploc bag                         10 mL DNA extraction buffer (soapy, salty water)

1 strawberry                                         glass rod, inoculating loop, or Popsicle stick

Cheesecloth funnel                             20 ml ethanol

50mL vial / test tube

Procedure:

1.       Place one strawberry in a Ziploc bag.

2.       Smash/grind up the strawberry using your fist and fingers for 2 minutes. Careful not to break the bag!!

3.       Add the provided 10mL of extraction buffer (salt and soap solution) to the bag.

4.       Kneed/mush the strawberry in the bag again for 1 minute.

5.       Assemble your filtration apparatus as shown to the right.

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

7.       Slowly pour cold ethanol into the tube. OBSERVE

8.       Dip the loop or glass rod into the tube where the strawberry extract and ethanol layers come into contact with each other. OBSERVE

Conclusions and Analysis

It is important that you understand the steps in the extraction procedure and why each step was necessary. Each step in the procedure aided in isolating the DNA from other cellular materials. Match the procedure with its function:

PROCEDURE

FUNCTION

A. Filter strawberry slurry through cheesecloth

___ To precipitate DNA from solution

B. Mush strawberry with salty/soapy solution

___ Separate components of the cell

C. Initial smashing and grinding of strawberry

___ Break open the cells

D. Addition of ethanol to filtered extract

___ Break up proteins and dissolve cell membranes

2.     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 wound thousands of threads together into a rope, it would be visible much further away. Is this statement analogous to our DNA extraction? Explain.

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

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

BIO 111: DNA Extraction: Strawberry

DNA Spooling

Explanation / Answer

Pre-lab questions:

1. Gene is the physical unit of heredity that transmits information from one cell to another and thereby one generation to another. DNA (deoxyribonucleic acid) is a double helical structure that looks like a twisted laddder; it contains the organism’s genetic information in the genes which lie along the structure of DNA.

2. DNA is present within the nuclues, covered by s nuclesr membrane.

Conclusions and analysis:

A. Filter strawberry slurry through cheesecloth -----> Separate components of the cell

B. Mush strawberry with salty/soapy solution ---------> Break up proteins and dissolve cell membranes

C. Initial smashing and grinding of strawberry --------> Break open the cells

D. Addition of ethanol to filtered extract ------------------> To precipitate DNA from solution

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