For a couple of months, I've had an idea for updating the Gene Expression Models I started creating a couple of years ago. There are three models: a lac-operon simulation, a model that illustrates the ways that two genes can interact to control the operation of a third gene, and a set of unknown problems for students to explore.
The unknown problems present a system of 5 genes to students. The students need to understand how the genes interact: which ones turn on or turn off the others.
I had figured out that there were three basic types of unknowns, those that: oscillate, run to fixation, or embody a race condition. In discussion with Randy, we had decided that there is also those that are self-initiating versus requiring a stimulus of some kind. In thinking about it, I decided that it was a useful diagnotic technique to be able to add some of each of the gene products independently. So I added a button that lets you squirt a little of each kind into the system. And I created one problem that doesn't do anything until you squirt something into it. I'm very happy -- it works great and adds a nice wrinkle to exploring these systems.