Do-It-Yourself Strawberry DNA



Name: ________________________

Period: 3 Date: 12/1Score: ____/50

DNA Extraction Lab

Pre-reading

Since DNA is the blueprint for life, everything living contains DNA. DNA isolation is one of the most basic and essential techniques in the study of DNA. The extraction of DNA from cells and its purification are of primary importance to the field of biotechnology and forensics. Extraction and purification of DNA are the first steps in the analysis and manipulation of DNA that allow scientists to detect genetic disorders, produce DNA fingerprints of individuals, and even create genetically engineered organisms that can produce beneficial products such as insulin, antibiotics, and hormones.  

DNA can be extracted from many types of cells. The first step is to lyse or break open the cell. This can be done by grinding cellular tissue in a blender. After the cells have broken open, a salt solution such as NaCl and a detergent solution containing the compound SDS (sodiumdodecyl sulfate) is added. These solutions break down and emulsify the fat & proteins that make up a cell membrane. Finally, ethanol is added because DNA is soluble in water. The alcohol causes DNA to precipitate, or settle out of the solution, leaving behind all the cellular components that aren't soluble in alcohol. The DNA can be spooled (wound) on a stirring rod and pulled from the solution at this point.

Strawberries, bacteria, humans—all living things have genes, and all of these genes are made of DNA. That's why scientists can take a gene from one living thing and put it into another. For example, they can put human genes into bacteria to make new medicines.

|Pre-lab Questions: |

1. Define lyse:

2. How is extracting DNA used in real life?

3. Define emulsify:

4. What type of material make up membranes? (You may need to use your textbook for this answer)

5. What is the purpose of the rubbing alcohol?

6. If human genes and bacterial genes are transferrable, what is an example of a helpful gene humans could benefit from?

Jobs: Materials: ______________________ Scribe: __________________________

Question: Will bananas or strawberries extract more DNA?

Hypothesis: (If..then… statement)

______________________________________________________________________________________________

Materials:

• 1 strawberries (green tops removed) and ¼ piece of banana (peels removed)

• 2 reclosable plastic sandwich bags

• 10 ml of DNA extraction buffer (keep at supply table)

• 2 Coffee filters (strainer)

• rubbing alcohol (kept in freezer)

• Dawn dishwashing liquid (keep at supply table)

• funnel

• 2 test tubes

• Stir stick

Procedure

1. Chill the rubbing alcohol in the freezer (Mrs. Ireland will have the alcohol in the freezer before class).

2. Put the strawberry in the plastic bag and push out all the extra air. Seal the bag tightly.

3. With your fingers, squeeze and smash the strawberry mixture for 2 minutes.

4. Put the banana in the plastic bag and push out all the extra air. Seal the bag tightly.

5. With your fingers, squeeze and smash the banana mixture for 2 minutes.

6. Add 10 ml of DNA extraction buffer to each bag. Seal the bag tightly and mix well for another minute.

7. Pour the strawberry mixture from the bag into the funnel through the strainer. Let the liquid drip into the test tube until there is no liquid left in the funnel. This separates the cells from each other, so you now have a really thin cell soup.

8. Add 4-5 drops of dish soap to the test tube and carefully stir with the stir stick.

9. Let the mixture sit for 5-10 minutes.

10. Pour the banana mixture from the bag into the funnel through the strainer. Let the liquid drip into the test tube until there is no liquid left in the funnel. This separates the cells from each other, so you now have a really thin cell soup.

11. Add 4-5 drops of dish soap to the test tube and carefully stir with the stir stick.

12. Let the mixture sit for 5-10 minutes.

13. Next, carefully add 5ml of ice-cold rubbing alcohol to each test tube. Since rubbing alcohol is less dense, the layers should not mix and the alcohol should be the top layer.

14. Dip the stirring stick into the test tube where the two layers meet. Slowly turn the stirring rod so DNA will wrap around the stick and can be removed. The white, stringy structure is DNA.

Observations (remember your 5 senses):

Results:

Conclusion: (answer the following questions on a separate sheet of paper: what is the purpose of the dish soap and meat tenderizer? In what fruit was more DNA extracted? Include mistakes made, observations, and include DNA key words). I am expecting a well written paragraph.

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Unit 6: Molecular Genetics

AP Biology: Mrs. Ireland

LAB

DNA Extraction Buffer:

1.5 teaspoons of meat tenderizer and 250 ml of water. Carefully mix and set aside.

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