Extracting DNA from Strawberries

DNA, or Deoxyribonucleic Acid, is the molecule of life. DNA exists in every single organism, from the smallest bacteria to the largest mammal, and is the only known molecule that has the ability to replicate itself.

DNA is a long fiber – like a hair – only thinner and longer. It is made from two strands that stick together with a slight twist. The DNA is organized into sections called genes and is coiled around proteins to form chromosomes. Genes can be turned on or off depending on the cell's needs.

California strawberries are the fruit of a genus of plants in the family rosaceae. There are more than 20 named species and many hybrids and cultivars, but the most common strawberries grown commercially are cultivars of the garden strawberry. Strawberries are also known as a nutritious “superfood,” packed with antioxidants, including Vitamin C. One serving of 8 medium-sized strawberries has only 45 calories and provides 140% of the US Recommended Daily Allowance (RDA) for Vitamin C, 210 mg of potassium, and almost 3 grams of fiber. 

Ripening is the process in fruit that causes them to become more edible. As in humans, plant hormones are chemical compounds that help regulate growth processes. Fruit grows as hormones make its cell walls more elastic and expandable. Other hormones break down chlorophyll, allowing bright, appealing colors to develop. Hormones decrease the acidity of the juice and convert complex carbohydrates in the tissue into sweeter simple sugars.

Materials:

1. 3 average sized under-ripe strawberries
2. 3 average sized ripe strawberries
3. 3 average sized over-ripe strawberries
4. 1/2 cup of tap water
5. 2 small, clear plastic cups
6. 2 measuring cups-1 teaspoon, 1 cup
7. Paper towels (use for drying your other materials, number may vary)
8. 2 teaspoons of dish detergent
9. 2 teaspoons of salt
10. 1 coffee filter
11. 1/3 cup of rubbing alcohol
12. Wooden popsicle stick
13. 1 plastic bag

Experimental Procedure:

STEP 1: Mix the DNA Extraction Liquid

1. Take 1 plastic cup and mix together 2 teaspoons of dish detergent.
2. Slowly mix in 1 teaspoon of salt.
3. Add 1/2 cup of water and mix.

STEP 2: Get the DNA

1. Take 1 strawberry and insert it into your plastic bag.
2. Using your hand, mash up the strawberry until there are no big chunks.
3. Add 2 tablespoons of the DNA extraction liquid.
4. Swirl gently using a wooden popsicle stick for at least one minute and then let it sit.

STEP 3: Separate the Fluids from the Solids

1. Take coffee filter and cover it over an unused plastic cup.
2. Pour the mix of strawberry and let it filter for 30 seconds or until the fluid has stopped dripping.

STEP 4: Extract the DNA

1. Next, pour down the side of the cup an equal amount of cold rubbing alcohol as there is strawberry liquid. Do not mix or stir.
2. Within a few seconds, watch for the development of a white    cloudy substance (DNA) in the top layer above the strawberry layer.
3. Tilt the cup and pick up the DNA using a wooden popsicle stick and put it into a measuring cup.

STEP 5: Measure the Amount of Extractable DNA

1. Record how much white content shows up in the measuring cup.

STEP 6: Repeat Process with Other Types of Strawberries

1. Rinse all plastic cups and other materials thoroughly with water and dry all materials using paper towels to avoid contamination.
2. Repeat this process with the other types of strawberries to determine which one produces the most visible DNA.