Preparation:

• Gather lab supplies
• Review and complete the entire lesson yourself so you can get a feel for the concepts and sequence. Jot down notes that will help the lesson flow smoothly with your students.
• Prepare to implement the following lab tips:
  • Encourage students to grind the mixture very well as this mechanical pulverization helps to break the cell walls.
  • Use masking tape and markers to label beakers and test tubes.
  • If the liquid from the mixture is not filtering through the coffee filter during step 6, you can gently squeeze the coffee filter to help strain the liquid. Make sure not to break the coffee filter.
  • Allow students some time to observe on step 10.
  • Put links to videos on class website (if applicable) or another place for students to access easily.

Activity 1: DNA Extraction Lab

1. Give each student one copy of the Strawberry Breeding and Genetics student handout.
2. Divide students into lab pairs and allow each group to complete the lab procedures outlined on page one:
   • Place one strawberry into the mortar and grind it with the pestle.
   • Add water, dish detergent, and salt to the mortar. Be sure the solution covers the strawberry. Continue to grind the mixture.
   • Label a beaker with your name. Place a coffee filter inside the beaker and use a rubber band to hold it in place.
   • Pour the strawberry mixture into the filter and place the beaker in the tray of ice. It’s important to keep the mixture COLD while it slowly filters.
   • While waiting for the mixture to filter, watch Video 1: DNA Extraction from "Part 2" of your worksheet. Answer follow-up questions 1-4. 
   • After the mixture has filtered, SAVE the filtered liquid (which contains the DNA) in the beaker. Discard the coffee filter and strawberry remains in the trash.
   • Label a test tube with your name. Pour the filtered liquid from the beaker into the labeled test tube.
   • Gently add twice the volume (5-10 mL) of 91% isopropanol (rubbing alcohol) to the test tube. Remember to layer the isopropanol on top of the clear liquid rather than mixing the two layers together. Watch and wait. Bubbles will begin to form and a white stringy substance will become visible.
   • Place the test tube back into the ice tray and check on it in 10 minutes. If you don’t stir the layers, a large “glob” of strawberry DNA will form. (Leave the tube in the ice for as long as possible.)
   • While waiting for the DNA to precipitate, clean your lab station and equipment and watch Video 2: In the Lab from "Part 2" of your worksheet. Answer follow-up questions 5-10.
3. Monitor student work continuously and engage students in reflection of what they are doing in each step of the procedures and why.
4. Make sure that students see the DNA product at the end of the class period.
   • Teacher Tip: Let each group view the videos on their own devices when they are ready. This is best accomplished during appropriate wait time in the lab procedures (steps 5 and 10), however, videos can be played at the front of the classroom at designated times if needed.
5. Be sure that lab pairs complete the follow-up questions after viewing each video in "Part 2."
6. Following the lab, lead a whole class discussion to compare and contrast how the student DNA extraction procedures are similar to and different from the DNA analyst in the video. Have lab groups compare their findings.
7. Direct students to work individually or in pairs to complete "Part 3: Post-Lab Reflections and Analysis" of the handout.
8. Facilitate a whole class discussion about why a scientist would want to extract DNA. Discuss with students that being able to extract DNA from a strawberry (or any other organism) is only a first step to examining its genetic make-up. 
   • “What can be done with my extracted DNA?"
     • This sample could be used for gel electrophoresis, for example, but all you will see is a smear rather than a band. The DNA you have extracted is genomic, meaning that you have the entire collection of DNA from each cell. Unless you cut the DNA with restriction enzymes, it is too long and stringy to move through the pores of the gel.
     • A scientist with a lab purified sample of genomic DNA might also try to sequence it or use it to perform a PCR reaction. But, your sample is likely not pure enough for these experiments to really work.
   • "How is DNA extraction useful to scientists? When do they use such a protocol, and why is it important?"
     • The extraction of DNA from a cell is often a first step for scientists who need to obtain and study a gene. The total cell DNA is used as a pattern to make copies (called clones) of a particular gene. These copies can then be separated away from the total cell DNA, and used to study the function of that individual gene.

Activity 2: Applying Strawberry Genetics to Agriculture

1. As a class, brainstorm all of the ways we consume strawberries. Make a list on the board. Examples include: jam, ice cream, yogurt, smoothies, whole berries, pie, chocolate covered strawberries, dried, etc. Once students have brainstormed, display the graphic below. 
2. Next, ask students if the strawberries with these different culinary uses need to have different traits or characteristics. Prompt students with the following examples of traits consumers are looking for when they purchase various strawberry products:
   • Color: Consumers prefer bright red berries. This is especially important after the strawberry has been processed into products such as jam, ice cream, yogurt, etc. Point out that a processed strawberry product is most appealing if it's a bright red/pink color.
   • Shelf life: Depending on climate, strawberries may and may not be able to be grown near to consumers. Strawberries should be able remain fresh long enough to be transported to consumers all over the country.
   • Size: Larger strawberries are ideal when making chocolate covered strawberries or when eating them whole. In the case of processed strawberry products, size does not matter as much.
   • Taste/sweetness: In all cases, strawberries should be sweet and not bitter. 
   • Preservability: Strawberries are often preserved by freezing. The berry should be able to be thawed and maintain most of it's color, taste, and appearance for best consumer appeal.
3. Explain to students that each of these traits are determined (or influenced) by the strawberry plant's genetics. The traits can be identified and perpetuated through the process of selective breeding.
4. Watch the America's Heartland episode, Sweet Sweet Strawberries. This 5-minute video highlights strawberry production at a California farm, describes how strawberries are selectively bred for specific traits, and explains how strawberries are packaged for shipping all over the United States.