This week, I co-taught an AP Biology class with one of our high school teachers. She was looking for a way to have students wrestle with the molecular structure of DNA, so I suggested a card sort activity.
[David Knuffke](https://twitter.com/davidknuffke) suggested the [Central Dogma sort from HHMI](https://www.hhmi.org/biointeractive/central-dogma-card-activity), but they weren't quite at the point of replication/transcription/translation. I ended up modeling its structure for our molecular sort. [Here's the Google Doc](https://docs.google.com/document/d/1Pv-iCEkZT09xGStWe6AL21tnYwT5wWJATrCqNTCQA0k/edit?usp=sharing).
This sort worked well for the students because they had already spent some time reviewing 3' --> 5' structure as well as the purine/pyrimidine relationship. Most of their work had been with simple block models at this point and I wanted to stretch them to think about the atomic interactions. We started by handing out just the pictures and giving pairs of students about three minutes to discuss and sort together. Here are three samples:
![Card sort group 1](https://photos.ohheybrian.com/uploads/big/330d31696c993a30fe574687fc4b7f9c.jpg)
*[Photo](https://photos.ohheybrian.com/#15436012063980/15436012697794) CC0 by Brian Bennett shared from Lychee.*
![Card sort group 2](https://photos.ohheybrian.com/uploads/big/cbb67e140d2b1b7af57a0633a49d9711.jpg)
*[Photo](https://photos.ohheybrian.com/#15436012063980/15436012655630) CC0 by Brian Bennett shared from Lychee.*
![Card sort group 3](https://photos.ohheybrian.com/uploads/big/f6207b0f698bd59e423ed76a9e7c86c9.jpg)
*[Photo](https://photos.ohheybrian.com/#15436012063980/15436012611074) CC0 by Brian Bennett shared from Lychee.*
Each group was able to explain their rationale to one another and to the class. There are similarities between groups 1 and 2. I _really_ loved that group 3 was almost the exact opposite of the first two groups, mainly to illustrate to the class that the _process of thinking_ is the critical piece to the exercise, not necessarily the 'right order.'
After groups felt good about their initial order, I handed the terms out and asked them to label each step. Connecting the visual to the language of DNA structure and introducing the idea of replication left us in a good spot for the day.
No matter how often I do card sorts, I never cease to be amazed at how _deep_ conversations get as students are putting cards in order. I think that's the challenge - getting a good set of images or graphics in place which promote those conversations without leading to a 'right answer,' especially in the AP context.
[The Google Doc](https://docs.google.com/document/d/1Pv-iCEkZT09xGStWe6AL21tnYwT5wWJATrCqNTCQA0k/edit?usp=sharing) with the cards and terms is is public, so feel free to grab it for your class if you're interested.