As the students enter class, they take out their journals and respond to the prompt:
Compare and contrast DNA and RNA.
While the students work on their journals, I circulate through the room, reading their answers and asking them to elaborate on their answers. I am also looking to see how many of them utilize a Venn diagram to answer this prompt. For many students, the words compare and contrast automatically trigger the use of a Venn diagram because we have discussed the association between those terms and the use of the diagram in previous lessons. I have the students use Venn diagrams because their use requires students to show the relationships between the items being compared. Sometimes when faced with a prompt like this, students focus more on definitions and will write the definition of DNA and the definition of RNA without really thinking about how they are alike and how they differ. Using the Venn diagram helps the students move beyond the definitions and into the concepts behind them.
Once the students have had an opportunity to complete their entry, I ask the class to identify a graphic organizer that can be used to compare and contrast items. Once they identify the Venn diagram, I draw one on the SmartBoard. I then call on students to come to the board and write either a similarity or a difference. After a student writes a similarity or a difference, I ask the rest of the class if they agree or disagree and to explain why. I encourage students to add a Venn diagram to the Cornell notes they finished prior to this class.
This is the video that the students take flipped notes on prior to this class period.
Conducting the journal discussion covers most of the information on the flipped notes the students completed. I review key terms from the flipped notes from the students, specifically pointing out the functions of mRNA and tRNA, because we will be focusing on them in an upcoming lesson. I also review the answers to the notes review with the students.
I then ask the students to take out their Chromebooks and open the Exploring DNA activity. I review the components of the activity with the students to ensure they understand the instructions and they begin working on the activity.
I have the students open the Exploring DNA worksheet on their Chromebooks as I open it on the SmartBoard. I review the guidelines of each section with the students to make sure they understand the instructions regarding the items that need to be completed during the lesson.
For the first activity, students are asked to visit a website to remind them about where DNA is found and the basic structure of DNA. This is to help prepare them to complete the second activity.
The second activity requires the students to build a model of DNA, using a model kit that I give them. I have two different types of DNA models, one is in the shape of a double helix, while the other is a flat, straightened version. A key part of this activity is that I do not provide the students with instructions for completing the model. They must work as a group and use what they know about the structure of DNA to create their models. While the students work on their models, I observe and question them, and provide assistance only when the students have reached high levels of frustration. Once the students have built their model, they take a picture of it and label the base pairs. Students are able to print their pictures or turn them in online.
In the third activity, the students visit a website and work individually to build a DNA molecule. This activity helps to reinforce the students' understanding of which bases pair together.
The fourth activity also requires the students visit a website to match base pairs of DNA. It is in a game format and once the students practice matching base pairs, they are then provided with the opportunity to read information about the number of chromosomes in different organisms. I use this activity as a way to help students understand that organisms differ in the number of chromosomes they have and to help them begin to understand the similarities and differences in the genetics of different organisms.
This video provides an overview of the websites used for this activity.
The activities in this section are designed to meet NGSS SP2 - as students develop and use DNA models; CCC Patterns - as students explore microscopic and atomic level structure; and build a foundation for MS-LS1-5 - as students explore DNA to later learn about the ways in which genetic factors influence the growth of organisms.
Near the end of the lesson, I call the students back together for a whole group review of the class activities. I focus primarily on the hands on model building portion of the class. Doing this helps the students describe the process of building the model and encourages them to recall the structure of DNA.
I ask the students to describe the process they used to build the models and, generally, the students with the three dimensional structure have the most difficult time. This discussion also enables students to hear about the construction of the model type that they did not have and allows for comparisons between the two. Additionally, the discussion allows for the exploration of the benefits and drawbacks of models as representations (CCC Systems and System Models Models are limited in that they only represent certain aspects of systems under study).