As the students enter the room, they take out their journals and respond to the prompt: Describe the DNA model that you built and explain the process you completed to build it.
Note: This prompt is based on the previous lesson DNA and RNA - Flipped.
As the students work on the prompt, I circulate through the room to read their responses. During this time I may ask them to add more detail or to explain a specific portion of their writing. I use question stems such as "How do you know?", "How would you organize ....to show...?", and "What would happen if you changed....?". While reading the students' work, I am checking for their understanding of how the model represented the structure of DNA by looking for the use of key words and phrases such as bases and double helix.
Once the students have had an opportunity to finish their writing, I ask for volunteers to share their journal with the class. As the students share their thoughts, I ask students to add to what has been said about the construction of the models. For instance, I ask students if they agree or disagree with what was said and then I ask them to support their stance. Sharing their journals allows not only for growth of understanding through collaborative thinking, it also leverages the power of revision as I encourage students to add to their journals while we discuss.
I explain to the students that since we have built a model of DNA and they have a general understanding of its structure, we are going to spend time exploring how DNA can be extracted from a cell and later we will explore some of the reasons why it is removed from cells. I ask the students to take out their Chromebooks and open the Online DNA Extraction activity. I go through the instructions with them as I use the SmartBoard to demonstrate the activity.
After reviewing the basic functions of the simulation with the students, they begin working independently to complete the simulation. While the students work on the activity, this is my opportunity to conference with students individually to determine their level of understanding regarding DNA. At this point in the unit, I expect them to be able to know what DNA stands for, be able to provide a general description of the function and the structure, with an emphasis on the base pairs. If students are unsure of any of this, I discuss the topic with them to determine what their misconception is and try to correct the misconception. I also ask the student to take out his/her notes, so additional explanations/information may be added to help provide clarity. Select the links to learn more about these common misconceptions and ways to overcome such misconceptions.
The completion of the online simulation and my individual conferences with the students help to lay the foundation for NGSS MS-LS-3 as students begin to understand the role that DNA plays within the cell and within the organism. While DNA extractions are not required by the standards, I use extractions as a bridge to our upcoming biotechnology unit and as a way to spark students' curiosity, especially since many science fiction films (like Jurassic Park) link to DNA.
This screencast describes the online simulation completed by the students.
This is a sample of proficient student work for this activity.
Near the end of class, I ask the students to share the information they wrote for the last question of their activity review worksheet. I call on one student at a time to share either a similarity or a difference with the class. I then ask for volunteers that agree or disagree with what has been said. These volunteers must support their ideas with evidence. This discussion of similarities and differences also provides a strong review for the online simulation activity, as students must recall the equipment and processes used in the simulation. This discussion also requires students to think critically about the items that we have access to in the lab and what types of items can be replaced with lower budget equipment, such as using a stirring rod instead of a centrifuge.