Module Goals include:
- To develop, in stages, the structure of DNA, using knowledge elicited from the students, then use the embodied structure to show how it facilitates replication (copying in preparation for cell division) and other functions of DNA (for more advanced students, transcription and molecular biology techniques)
- To understand the difference between covalent and hydrogen bonds, and the power of the information contained in the bases and the specificity of their hydrogen bonds.
- To cause the students to ask new and different questions about DNA structure, as they see gaps in their knowledge as they try to build the model with their bodies.
CMT Goals
Background
- Most students, from at least 7th grade, have ideas about DNA structure — the double helix, perhaps with 4 kinds of bases and basepairing. From this, they can start modeling the structure. The teacher then adds more and more facts about the structure, such as the difference between the hydrogen bonds of A-T and C-G basepairs, and the antiparallel relationships of the two strands, which become constraints the students must incorporate into their embodied model.
- Several toolbox activities are used in the beginning of this module, to bring to mind their own knowledge of and associations with DNA and bonding, and to prepare the students to use their bodies in modeling the structure.
- This module can work well either to introduce DNA structure at the beginning of a unit on DNA, or to sum up, show gaps, and then solidify knowledge near the end. Advanced students can move on to replication, transcription molecular techniques using hybridization, such as Southern blots and PCR.
Activities – (details in lesson plan):
- Guidelines for participation — how to be comfortable touching each other
- Warm-up 8-4-2-1
- The Ask A Question tool encourages students to bring to mind what they already know about the subject, and make personal associations
- What did you have for breakfast this morning?
- What do you see in your mind when you think about DNA?
- What do you think of when I say the word BONDS?
- With whom are your closest bonds?
- An exercise in different kinds of connections between two students — tight, loose, different parts vs same parts, sharing weight symmetrically vs asymmetrically, prepares students to think about the different kinds of bonds (covalent vs hydrogen) and the parts they play in the DNA structure.
- In groups of 8 – 12, students build the DNA structure with their bodies, sequentially incorporating additional facts about the structure provided by the teacher. First, they work out the basic shape of the ladder (unwound helix) and the orientation of the covalent and hydrogen bonds, then differentiate between C-G and A-T basepairs, then add directionality. Between additions, the different groups observe and comment on each others’ structures.
- When the final antiparallel, properly base-paired structure is complete, the teacher unzips the helix (breaks all the hydrogen bonds) and separates the strands of one of the groups, and invites the other groups to break up into single subunits (bases) to remake the opposite strand, using the existing strand as template, showing how the structure of DNA facilitates its own replication.
- Students reflect on the experience orally or in writing. (click to download sample reflection prompts)
Resources
Evaluation
- Homework assignment: student reflections on the classroom experience; discussion of validity of their structure, compared to known facts about DNA structure — see examples of student reflection feedback forms
Additional Comments
- This module has worked well with 7th graders through advanced college students. It helps to be able to push tables and chairs out of the way, to make an open space to move in the classroom.
- It would be hard for a single teacher to do this with more than 36 students (three groups of 12).
- The teacher should be actively listening as the students build the DNA structure, to hear and repeat to the whole class good questions or observations the students make to each other while trying to make their model, or push students to find the answers to the questions they raise.
- Frequent stops to have one group comment on another’s structure cause students to think more carefully about what the different parts are doing, and how many different representations can give the same meaning.
- This session lends itself well to a discussion of the role of model building in science. Is the embodied learning they just did science? Did Watson and Crick do experiments, or just use other peoples’ data? Is a model a failure if it is not a perfect representation? Can all models be fine-tuned to incorporate new data, or is it the sign of a robust model? Can their model be used to make testable predictions?
FAQ
- [Frequently asked questions will be added here based on feedback]
Modified on: Apr 19th, 2011 Log in
