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Strawberry DNA Extraction Lab

Students will learn about DNA and genetics through this 8th grade lesson.

Jonathan Bailey

The Arizona STEM Acceleration Project

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Notes for teachers

When the students are ready to smush the strawberries, have them work with a partner to hold the quart ziploc bag while the other student pours in the buffer solution.
Instruct students to make sure the seal on the ziploc bag is tight before gently smashing the substances together. Place the quart ziploc bag into a gallon ziploc bag for extra protection.
Students may have difficulty gently squeezing the strawberry & buffer solution liquid in the coffee filter. If the coffee filter breaks, have extra coffee filters handy.

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List of Materials

Materials

Dish soap, baking soda, iodized salt, 2 oz plastic portion cups, 6 inch wooden skewer, coffee filter, 8 oz plastic container, quart size ziploc bag, plastic plate or plastic tray, disposable plastic table cloths, paper towels, safety goggles, disposable lab apron (optional), latex free gloves, isopropyl alcohol, fresh strawberries, a plastic test tube.

Math Connection Recording Sheet: Click here

Buffer solution

200 mL water
one half teaspoon of salt
1 teaspoon of baking soda
1 teaspoon of dish soap

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Standards

Arizona Science Standards

8.L3U1.9 Construct an explanation of how genetic variations occur in offspring through the inheritance of traits or through mutations.

Math Standards

8.SP.A.1 — Investigate patterns of association in bivariate data.

ELA Standards

8.W.4 Produce clear and coherent writing in which the development, organization, and style are appropriate to task, purpose, and audience.

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Objective:

Today we will extract DNA from strawberries and identify the DNA within them.

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Agenda (90 minutes)

Day 1 - Engage

Strawberry DNA Extraction Lab

Lab Reflection

What went well?
Which part was a challenge for you?
What would you change if you could do this lab again?

Day 2 - Construct an Explanation

Write a 5-7 sentence paragraph that answers the question: What is DNA and how does this lab activity relate to genetics?

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Intro/Driving Question/Opening

What is DNA and what does it have to do with genetics?

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Hands-on Activity Instructions

Create the buffer solution.

200 mL water
one half teaspoon of salt
1 teaspoon of baking soda
1 teaspoon of dish soap

Students will then carefully smush two strawberries in a quart ziploc bag and add 50 mL of the buffer solution. Do this for 2 minutes.
Then, put the smushed strawberries into a coffee filter and let it drip out over the 8 oz plastic container. Make sure to get as much strawberry liquid as you can.

After that, pour the strawberry and buffer solution into your plastic test tube (fill it to the 50 mL line).
Add the ice cold isopropyl alcohol to the test tube. Leave space at the top of the test tube.
Hold the test tube and let it set for 5-10 minutes.
Use your six inch wooden skewer to swirl around the liquid in the test tube to gather the DNA.
Each student will complete this activity. Allow them to work with a partner throughout the activity if needed.

Math Connection: Recording Sheet

Amount of DNA extracted (mL or visual estimate)� vs.�
Type of fruit, temperature of mixture, or extraction time�

They’ll record the data, plot it, and look for patterns such as:

“Do longer extraction times lead to more DNA?”�
“Which fruit produced the most DNA?”

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Assessment

Students will successfully complete the Strawberry DNA Extraction Lab. Each student will be able to follow procedures and extract DNA using the supplies provided.

Math Connection: Recording Sheet

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Differentiation

Remediation

Extension/Enrichment

Have students use the Strawberry DNA Extraction Protocol step-by-step instructions to help them do the activity.

Walk around and monitor students.

For the math portion, you can choose to do it together as a class if it seems students are struggling. I would also team up with the math teacher in order to see what students have already learned.

Let the students look up videos about DNA and Genetics that look interesting to them.

Have the students draw a picture of each step that took place during the extraction lab activity.