DNA Extraction

All living things have DNA, from insects to animals to plants. In today’s lesson, we will extract DNA from a strawberry.

Chill the rubbing alcohol in the freezer for at least an hour before the experiment to ensure it's cold enough to help precipitate the DNA.

Fresh strawberries

Dish soap

Table salt

Water

Ziplock bags

Coffee filters or cheesecloth

Small clear plastic cups or test tubes

Rubbing alcohol (chilled)

Measuring spoons and cups

Wooden skewers or toothpicks

1. Introduction to DNA (10 minutes)

Discuss the concept of DNA, explaining its role as the blueprint of life and its presence in all living cells.

Introduce the objective: To extract and observe DNA from a strawberry.

2. Strawberry DNA Extraction Procedure (30 minutes)

Step 1: Preparation (5 minutes)

Mix 90 ml of water, 10 ml of dish soap, and a teaspoon of salt to make the extraction solution.

Place a strawberry in a Ziplock bag, add 10 ml of the extraction solution, and seal the bag.

Step 2: Mashing (5 minutes)

Gently mash the strawberry in the bag for 2 minutes, ensuring the fruit is thoroughly crushed.

Step 3: Filtration (5 minutes)

Place a coffee filter or cheesecloth over a cup and pour the strawberry mixture into the filter to separate the liquid from the solid parts.

Step 4: Precipitation (15 minutes)

Add equal parts of the filtered strawberry liquid to a small clear cup or test tube.

Tilt the cup and slowly pour chilled rubbing alcohol down the side so that it forms a layer on top of the strawberry liquid.

Observe as the white, stringy DNA o precipitates out into the alcohol layer.

Use a wooden skewer or toothpick to gently spool the DNA.

3. Discussion and Reflection (10 minutes)

TtyyyyyyttyyyyyyttttDiscuss the results, focusing on how DNA looks and feels.

Reflect on the importance of DNA in genetics and molecular biology.

Explore questions students have about DNA, genetics, and the experiment.

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