This lesson uses the engineering design process and scientific models to teach students the structure of DNA. It is structured to begin a unit on DNA in a high school biology course. 

Hook and PreAssessment - Student Created Models

Working individually or in pairs, instruct students to build a model of DNA based on their own prior knowledge and/or individual research using your choice of provided materials. Give them approximately 10 minutes to build their models, and do not give them anything other than the building materials. If students are concerned that their model is/will be "wrong", tell them this is fine for now. This is just to see what they remember. Tell them to do their best, and they will have a chance to make adjustments to their model later prior to grading. Suggested material for building the models: clay or modeling dough, toothpicks or small straws/coffee stirrers/sticks, colored circle shaped fruit cereal, mini marshmallows, etc. Use whatever materials you have on hand that would allow students to make a quality model. 

Part 2 - Model Gallery Walk

Once the students have made their own models, allow them to circulate around the room looking at some provided models that were set up while they worked. Be sure to provide a variety of different DNA models including at least one 3-D model (such as the bead type building models or DNA origami), a 2-D model (such as a printed paper models), and a virtual model (such as a QR code that links to an online video about DNA structure). Students can also visit other groups and view other student models during this time as well. As they circulate, students need to take note of the similarities and differences in the models. What common features do they see? Which model(s) contain(s) the most detail? Which model do they think provides the best instruction on the structure of DNA and why?

After students have had sufficient time to complete the gallery walk and questions, come back together as a group to discuss/review/learn the key features of DNA: the phosphate-sugar backbone, the base pairing between nitrogen bases, the double helix structure, etc. As you are teaching each key feature, point it out on each of the teacher provided models so that the students can visualize the item in multiple ways. Once the instruction has ended, have students modify their own models at this point to make sure that all of the key features are represented. Give them a list of features that must be featured on their model for grading, and allow them to make modifications as needed.

Part 3 - Peer Assessment

Now have students assess one another's models to identify the presence of the listed key features. They should give one another feedback on which key features were present and which may be absent. If a group is missing a key feature, the assessing students can provide ideas/direction for how to include the missing element prior to teacher grading.