You should already have completed Steps 1-4 on the Week 2 Assignment Deliverable Template using the instructions from Week 2’s DNA from Fruit page before starting the activity below.
Read all the instructions below before starting the activity.
Step 1: Wash your hands and your work surface.
Step 2: Collect and prep your materials.
- Bananas
- Strawberries
- 2 ziptop plastic bags
- Measuring spoons and cups
- 2 clear narrow glass cups or jars
- Knife
- Table salt
- 1 16oz bottle 70% isopropyl alcohol – stored in freezer for at least 1 hour BEFORE the experiment
- 1 cup room temperature water – stored at room temperature for at least 1 hour BEFORE the experiment
- Liquid dishwashing detergent (i.e., Dawn Dish Soap)
- Coffee filters (paper towels can be substituted)
- Toothpicks, wooden skewers, or coffee stirrers
- Optional equipment: food scale, ruler, rubber bands, string
Step 3: Measure out equal amounts of each fruit.
- Cut a 1-2” section of peeled banana.
- Cut an equal amount of strawberries.
- Ideally, you’d use the food scale here to be sure you have the same amount of each fruit.
- You can “eyeball” it, if necessary, but recognize that it might skew your results if you have more of one fruit than the other.
- Take a picture of your prepped fruits side by side.
- Write down any thoughts, questions, or observations you have at this step.
Step 4: Insert fruit into bags.
- Place the banana section in one bag.
- Place the strawberries in another bag.
- Using your fingers, knead and squeeze the fruits until no solid clumps remain.
- Take a picture of the fruit pulp bags, side by side.
- Write down any thoughts, questions, or observations you have at this step.
Step 5: Add salt water and dishwashing detergent.
- Add 2 teaspoons of salt to your 1 cup of room-temperature water.
- Stir until salt is completely dissolved.
- Pour ½ cup of the salt water into each bag.
- Seal tightly.
- Mix each bag by shaking gently for 45 seconds.
- Add 1 teaspoon liquid dishwashing detergent to each bag.
- Seal tightly.
- Mix each bag by shaking very gently for 45 seconds (you do not want to create foam).
Step 6: Attach the coffee filter.
- Place a coffee filter over the top of each empty glass.
- Push the center of the filter down into the top of the glass to create a small well.
- Secure the filter with a rubber band or string.
Step 7: Pour the fruit mixture into the glasses.
- Slowly pour the banana mixture into one of the glasses through the filter in small batches.
- The fruit solids will be trapped by the filter.
- The liquid containing the DNA will filter into the glass.
- It may take several batches to get all of it from your bag into the glass.
- If your filter becomes too clogged with solids you can replace the filter with a clean one.
- Be patient, it takes time for all the liquid to filter through.
- Repeat this process with the strawberry mixture.
- Remove the filters.
- Take a picture of your glasses side by side.
- Write down any thoughts, questions, or observations you have at this step.
Step 8: VERY slowly add the ice-cold alcohol.
- Tilt each glass at an angle and very, very slowly pour the ice-cold alcohol down the inside of the glass such that the alcohol does not mix with the liquid but forms a 1-2” layer on top of the DNA liquid.
- Take a side-by-side image of your layered glasses.
- Write down any thoughts, questions, or observations you have at this step.
Step 9: Observe, part 1
- Watch the interface between the alcohol and the DNA mixture for at least 10 minutes.
- You will notice that a cloudy, clumpy, stringy substance will begin to accumulate.
- Take a side-by-side image of your DNA extraction at 10 minutes.
- Write down any thoughts, questions, or observations you have at this step.
- Leave the glasses alone for 1 hour.
Step 10: Observe, part 2
- Using the toothpick or skewer to gently swirl the top section of each glass and lift to observe which has more DNA.
- Take a final side-by-side image showing the full glass and your DNA covered toothpick.
- Write down any thoughts, questions, or observations you have at this step.
You have collected your data! Now it is time to document and finish the remaining steps of the Week 2 Assignment Deliverable Template using the instructions on the DNA from Fruit page.
Submission Instructions:
- Submit a completed version of the Week 2 Assignment Deliverable Template in either .docx or .pdf format.
- Do not remove anything or change this template other than to add the requested information or images.
- Your images should be embedded in the document, not submitted as separate files.