Extracting DNA from Strawberries
Grade Level: Middle School; Type: Life Science
Determine which stage of the strawberries would be the most easy to extract DNA from, under-ripe, ripe, or over-ripe.
DNA, or Deoxyribonucleic Acid, is the molecule of life. DNA exists in every single organism, from the smallest virus 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 stretches of genes where proteins attach to coil the DNA into chromosomes, stretches that “turn a gene on” and “turn a gene off”.
California strawberries, are a genus of plants in the family rosaceae, and the fruit of these plants. 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.
- 3 average sized under-ripe strawberries
- 3 average sized ripe strawberries
- 3 average sized over-ripe strawberries
- ½ Cup of tap water
- 2 small, clear plastic cups
- 2 measuring cups-1 teaspoon, 1 cup
- Paper towels (use for drying your other materials, number may very)
- 2 teaspoons of dish detergent
- 2 teaspoons of salt
- 1 Coffee Filter
- 1/3 cup of Rubbing Alcohol
- Wooden Popsicle Stick
- 1 Plastic Bag
STEP 1: Mix the DNA Extraction Liquid
- Take 1 plastic cup and mix together 2 teaspoons of dish detergent
- Then take1 teaspoon of salt in mix in slowly
- After take ½ cup of water and mix.
STEP 2: Get the DNA
- Take 1 strawberry and insert it into your plastic bag
- Using your hand, mash up the strawberry until there is no big chunks
- Add 2 tablespoons of the DNA extraction liquid
- Swirl gently using a wooden popsicle stick for at least one minutes and then let it sit
STEP 3: Separate the Fluids from the Solids
- Take coffee filter and cover it over an unused plastic cup
- Pour the mix of strawberry and let it filter for 30 seconds or until the fluid has stopped dripping
STEP 4: Extract the DNA
- 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.
- Within a few seconds, watch for the development of a white cloudy substance (DNA) in the top layer above the strawberry layer
- 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
- Record how much white content shows up in the measuring cup using a measuring cup.
STEP 6: Repeat Process with Other Types of Strawberries
- Rinse all plastic cups and other materials thoroughly with water and dry all materials using paper towels to avoid contamination
- Repeat this process with the other types of strawberries to determine which one is the most extractable to get DNA.
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