California Agriculture in the Classroom

DNA: Expressions in Agriculture

Grade Level(s)

6 - 8

Estimated Time

Two 45-minute sessions

Purpose

This lesson centers around the activity of extracting DNA from a strawberry while highlighting careers in biotechnology and agriculture.

Materials

Activity 1:

*These items are included in the Strawberry DNA Necklace Kit, which is available for purchase from agclassroomstore.com.

Activity 2:

 

Essential Files (maps, charts, pictures, or documents)

Vocabulary

deoxyribonucleic acid (DNA): the heredity material in humans and almost all other organisms; similar to a “blueprint” of guidelines that a living organism must follow to exist and remain functional

genetic engineering: the process of manually adding DNA to an organism with the goal of adding one or more new traits not already found in that organism

genetically modified organism (GMO): any organism developed through a process in which a copy of a desired gene or section of genetic material from one organism is placed in another organism

Did you know? (Ag Facts)

Background - Agricultural Connections

Prior to this lesson students should have a basic understanding of cells, cell organelles and their functions, and the structure of DNA.

Although principles of biotechnology have been in use for over 6,000 years, the scientific field of biotechnology is relatively new. Biotechnology can be broadly defined as the use of living organisms or biological processes to make a product. Applications of biotechnology include using microorganisms to clean oil slicks, finding cures for human diseases by identifying related DNA sequences, and improving crop yields by transferring DNA from one organism to another to modify the genetic makeup of that organism.

Gregor Mendel was the first person to trace the characteristics of successive generations of a living thing (peas), and his discoveries laid the foundation for biotechnology as it is practiced today. Mendel was not a world-renowned scientist in his day. Rather, he was an Augustinian monk who taught natural science to high school students. His discovery of trait transfer was, at first, a theory. Genetic theory is no longer questioned in anyone’s mind. Many diseases are known to be inherited, and pedigrees are commonly traced to determine inheritance patterns of disease. Plants are now designed in laboratories to exhibit desired characteristics. The practical results of Mendel’s research not only changed the way we perceive the world but also the way we live.

The modern processes of biotechnology allow scientists to select what types of traits an organism will have and create changes that would otherwise happen slowly, over many seasons in the field. In agriculture, biotechnology is being used to increase crop yields, produce insect- and weed-resistant plants, and enhance vitamin and mineral content in food. It is also used to increase milk production and make cheese. Many of these advancements have been achieved by directly manipulating the DNA of plants and microorganisms, a process known as genetic engineering. Plants and microorgansims with genetically engineered DNA are called genetically modified organisms (GMOs). The process of transferring genetic information between plants was developed in 1973, and there is still debate regarding the benefits and risks of GMOs.

In this activity, students will model a process that scientists use to extract DNA strands. Deoxyribonucleic acid (DNA) is a long molecule that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. Yes, DNA is in all your food! The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints, a recipe, or a code because it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but DNA contains more than just genes. Other DNA sequences are involved in regulating the use of this genetic information, and others have structural purposes. For more information about genetics and easy to understand tutorials, visit the Genetic Science Learning Center.

In this lab, students will extract strands of DNA from the nuclei of strawberry cells. Mashing the strawberries will break the cells’ walls, exposing the inner membranes. The DNA extracting solution will disrupt the cell and nuclear membranes. Filtering the mixture gets rid of all the strawberry cell parts that are bigger than DNA. Finally, the alcohol causes the DNA to precipitate and come out of the solution. Participating in the extraction of DNA will help familiarize students with one aspect of the work biotechnologists do.

In terms of careers, a plant scientist or genetic engineer may use biotechnology as a tool; these scientists may also employ biotechnologists. Biotechnologists have diverse and interesting careers. They work with living organisms in manufacturing and industrial settings. Often biotechnologists do not work with the complete plant or animal, but rather focus on cells, tissues, and even microorganisms that may be contained within the larger plant or animal structure. Often, a biotechnologist works in a laboratory setting under carefully controlled conditions to make changes to the minute systems that exist within a single cell.

Biotechnologists can be hired to help develop new medicines and medical treatment options, assist in waste treatment or environmental remediation, or develop new characteristics in livestock and plants for agricultural use. Biotechnologists work in many different sectors, including hospitals and research facilities, private food or animal production companies, pharmaceutical companies, government agencies, and food processing plants. They come from backgrounds in science and engineering or a combination of several educational groups including chemistry, biochemistry, microbiology, life sciences, and pharmacy sciences.

This lesson plan is one of eleven that are approved by the Utah State Office of Education (USOE) for teaching agriculture content in the College and Career Awareness course. The suggested sequence for these lessons follows.

First:

Early (any order):

End (any order):

Last:

 

Interest Approach – Engagement

  1. Tell your students that you are thinking of a specific food, you are going to give them a list of clues, and you want them to guess which food you are thinking of. Ask students to raise their hands when they think they know the answer.
    • This food comes from a perennial plant.
    • In the United States, California grows the most of this food.
    • This food is usually red but can also be yellow or white.
    • This food has seeds on the outside.
    • This food is a fruit.
    • This fruit provides vitamin C to our diet.
    • What is this fruit? Strawberries!
  2. Display the image below of various types of strawberries. Ask your students to list the similarities and differences they see among the pictures. Help students recognize that various colors, sizes, and shapes of strawberries exist. Strawberries are usually red, but they can also be white and yellow. Strawberries can also be small or large and oblong or round. 
  3. Point out to the students that while these strawberries have different characteristics, they are all still strawberries. Ask the students, "What makes each of these strawberries different?" Provide further guiding questions and draw on students' prior knowledge of genetics and traits to help them recognize that the DNA in each of these strawberries is slightly different, leading to variation in characteristics.
  4. Explain that strawberry farmers and plant breeders work together to create varieties of strawberries that meet our needs. 

Procedures

Activity 1: Strawberry DNA Extraction

  1. Prepare the DNA extracting solution the day before the activity. 
  2. Review and discuss the information provided in the Background with students. Pass out a Strawberry DNA Extraction Lab activity sheet to each student.
  3. Divide students into groups of three or four and provide each group with the following materials: Ziploc bag containing 3 strawberries and 3 tablespoons of DNA extracting solution, funnel, plastic cup, 2 squares of cheesecloth, graduated test tube, pipette, test tube, 3–4 microcentrifuge tubes (1 per student), and 3-4 pieces of yarn (1 per student). 
  4. Guide students through the following instructions, which are also provided on their lab activity sheets:
    • Collect your materials.
    • Carefully remove most of the air from the Ziploc bag, and seal it well.
    • Gently mash the strawberries through the bag. Be careful not to break the bag, but mix the strawberry mash thoroughly.
    • Place the funnel in the plastic cup. It should sit on the rim of the cup.
    • Place the two squares of cheesecloth into the funnel, forming a liner for straining.
    • Carefully pour the strawberry mixture into the funnel, making sure to catch the solids with the cheesecloth. After filtering the mixture, remove the cheesecloth, and place it into the Ziploc bag for disposal.
    • Add 5 ml of the filtered strawberry extract to the graduated test tube using the funnel. Hold the tube near the top so that the heat from your hand does not affect the extraction.
    • Remove the funnel, and use the pipette to forcefully add 3 ml of the isopropyl or rubbing alcohol to the test tube. Take care not to tilt or tip the test tube; do not mix the two liquids.
    • Observe the line between the strawberry mixture and the alcohol. You will notice a white, thread-like cloud appearing at this line. This is the strawberry DNA. The DNA will clump together and float to the top of the alcohol layer.
    • Holding the tube still, observe the tubes of others around you. Do you notice any differences?
    • Using the pipette, add some DNA strands and some of the alcohol in the test tube to each person’s microcentrifuge tube. Repeat steps 6 to 8 if necessary to collect enough DNA for everyone’s microcentrifuge tube.
    • Close the cap of the microcentrifuge tube tightly around a piece of yarn and tie the ends of the yarn to make a necklace.
    • Clean up! Dump the remaining strawberry solution where instructed, throw away the Ziploc bags, and collect the cups, test tubes, funnels, and pipettes to clean so they can be used again.

Activity 2: Careers in Biotechnology

  1. Provide each student with the Biotechnology WebQuest activity sheet, and instruct them to answer the questions on a separate sheet of paper.
  2. Review the students’ responses to the activity sheet.
  3. Ask students what kinds of careers in biotechnology would rely on DNA extraction. Guide the conversation so that students make a connection between the DNA they have extracted and the scientists who rely on similar methods to research and create genetically modified organisms (GMOs). 
  4. Ask students about some of the pros and cons of biotechnology.
  5. List careers that would use biotechnology tools and information. 

Concept Elaboration and Evaluation
After finishing the activities, review the following key concepts:

Enriching Activities

Suggested Companion Resources

Sources/Credits

  1. http://www.ers.usda.gov/webdocs/publications/err162/43667_err162_summary.pdf

Author(s)

Debra Spielmaker and Denise Stewardson

Organization Affiliation

Utah Agriculture in the Classroom