Name:Block:

Strawberry DNA Extraction

Background: Cells are the basic unit of life and make up all plants, animals and bacteria. DNA is the molecule that controls everything that happens in the cell. DNA contains instructions that direct the activities of cells and, ultimately, the body. This DNA is organized into chromosomes located in the nuclei of all plant and animal cells. Strawberries have eight copies of each chromosome whereas humans have only two copies. As a result strawberries contain a large amount of DNA that can easily be isolated and viewed with the naked eye.

Objective: To show that DNA can be isolated from strawberries and see a large sample of DNA.

MATERIALS:Materials for the lab are set up in a bin for your group. Please ensure that everything is cleaned and returned to your bin. The alcohol is an ice bath to keep it cold. Collect some ethanol in a small beaker when required.

o Ice cold DNA extraction solution (5 mL dish detergent, 2.5 mL table salt and 25 mL cold water) This solution is used to ____________________________________________________________

______________________________________________________________so DNA is released.

Salt in the solution helps the DNA______________________________________by attracting the

____________________ DNA

o One frozen strawberry, 1 ziploc bag, 1 test tube and rack , 25 mL graduated cylinder filled with cold water, 1 paper clip, 1 piece of paper towel, small beaker, funnel, 2.5 mL salt, and 5 mL dish soap

o ICE cold ethanol in small beaker (5-10 mL) – pour extra back into original beaker

PROCEDURE:*Reminder: Do not eat the strawberries or anything else in this lab.

1. Put your frozen strawberry into the plastic bag. Put extraction solution ingredients into the graduated cylinder, mix carefully and pour into bag containing strawberry.

2. Seal the bag and gently crush the contents inside (try not to damage the bag or otherwise make the contents leak out). Make sure the strawberry is completely broken down (this may take quite some time).

3. Let sit for 5 min. at room temperature.4. Open the bag at one end, creating a spout. Use a funnel and fill your test tube with the liquid

up to the half-way point on the tube.5. Collect enough cold ethanol into the small beaker to fill the test tube to ¾ full. (approx. 5 mL)

6. Observe DNA beginning to collect in the interface layer between the alcohol and strawberry solution.

7. Using the paper clip, form a hook and try to fish the DNA out and onto a paper towel.

8. Clean up all the equipment you have used. Pour the strawberry solution into the garbage can, and rinse the test tube in the sink along with other glassware used. Throw out the paper towel with DNA sample, Ziploc and remaining strawberry solution.

9. Place rinsed paper clip, beaker, graduated cylinder, funnel and test tube back in bin.10. Wash your hands.

Questions:1. Why is it important for the liquids used in this lab to be cold?__________________________

____________________________________________________________________________

2. Why do you think it was necessary to crush the strawberries in this demo? ______________

____________________________________________________________________________

3. What step was required to finally make the DNA visible?______________________________

____________________________________________________________________________

4. Describe the appearance of the DNA. Is this what you expected? Explain. _______________

____________________________________________________________________________

____________________________________________________________________________

5. Do you think the DNA from another organism might have a different appearance? Why or why not?____________________________________________________________________

____________________________________________________________________________

DNA MODEL FOLLOW UP QUESTIONS:

1. The structure of DNA is actually in a DOUBLE HELIX arrangement.

DOUBLE HELIX means that the two long chains of nucleotides are arranged in a spiral like a twisted ladder.

The sides (or "uprights") of the ladder are made up of alternating _____________ and _____________ molecules. The steps (or "rungs") of the ladder are made of _______________ bases that are connected by hydrogen bonds.

2. A nucleotide consists of one _____________ molecule bonded to a sugar molecule which is bonded to one ________________base.

3. A real DNA molecule consists of THOUSANDS of paired nucleotides. What is the pairing arrangement of the nitrogen bases?

_____________ pairs with ____________ and _____________ pairs with ____________

4. Are there always going to be an EQUAL number of adenine and thymine nucleotides in a molecule? Why?

5. Are there always going to be an EQUAL number of guanine and cytosine molecules in a molecule of DNA? Why?

6. Scientists abbreviate the nitrogen bases by using the first letter of each base. So,A always binds to ____G always binds to ____

7. In the space below, complete the other strand of DNA for the provided sequence of bases.

Sequence: T A C G T A T G A A A C

8. A single gene codes for a single protein. A gene typically contains hundreds to thousands of base pairs. The gene code is read in 3 letter segments (codons – GAG TCA CAT) to create amino acids, the building blocks for proteins. This nine letter segment would code for the amino acids: Glutamine-Serine-Histidine.

If we were to connect all the DNA models made in this class into one lone DNA molecule how many base pairs would there be in this larger DNA molecule?

Would this longer DNA molecule be an example of a typical “gene”?

Bonus: If there are only 120 base pairs in a gene, the first and last three base pairs are used to indicate the start and end of a protein, what is the maximum number of amino acids that would make up this protein?

CONCLUSION:In a paragraph, write what you discovered in completing this lab. What did you learn? What went as expected? What surprised you? What did you learn about DNA?