Group Names: _________________________

_________________________

Date: _____________

Extracting DNA from strawberries

You will need, for one extraction:

- 1 zip lock bag

- 1 piece of strawberry

- 2 teaspoons DNA extraction buffer (salt and dishwashing liquid)

- cheesecloth

- Funnel

- Ice cold Isopropyl rubbing alcohol

- Test tube

- Long Cocktail stick

What to do: (3 points for each QQ, 10 points for each observation)

QQ1: What barriers will we have to get through to get to the DNA out? ______________________________________________________________________________________

Step 1. Place the strawberry in a zip lock plastic bag and crush it with your fist

QQ2: Why do you have to crush the mixture before you are able to extract the DNA? ______________________________________________________________________________________

Step 2. Add 2 teaspoons of the DNA extraction buffer to the bag, zip it up and squeeze it in your hands for 1 minute

QQ3: What do you think the salt in the buffer will do to the strawberry? ______________________________________________________________________________________

QQ4: What do you think the dishwashing liquid in the liquid is used for? ______________________________________________________________________________________

Observation 1: Record what the mixture looks like before pouring it into the funnel.

Step 3. Place a funnel in the test tube. Place the filter paper in the funnel.

Step 4. Pour the strawberry-shampoo mixture into the filter paper. Filter the mixture into the tube.

QQ5: What are you collecting by pouring the mixture through filter paper? ______________________________________________________________________________________

Step 5. Carefully pour ice-cold alcohol into the tube, until it is about half full. The alcohol will form a layer on top of the filtrate.

QQ6: Why do you think the alcohol should be kept ice cold? ______________________________________________________________________________________

Step 6. Keep the tube still at eye level; do not shake it.

Observation 2: Watch and record what happens.

Step 7. Scoop out the DNA with the cocktail stick.

Wrap-up Information:

Crushing the strawberries breaks open many of the strawberry cells, where the DNA is. The soap in the shampoo in the extraction buffer breaks down the membranes of the cells, releasing the DNA. The salt makes the DNA molecules stick together, and separate from the proteins that are also released from the cells. The filter paper will retain cell debris and unmashed pieces of fruit. The DNA will pass through the filter paper into the test tube. DNA is not soluble in alcohol, so it precipitates. What you see are long, rope-like DNA molecules in the alcohol.

Conclusion (20 points):

Write a short reflection on the process of DNA extraction. Include why we would need to do this procedure in science, what are the general steps, and why we used strawberries (instead of something else). Give at least 2 real-world examples of when this would come in handy.