Which part of the living system did you change?
Labs / Biology
Gene Switch (Lac Operon)
This is how a bacterium decides whether to make the enzymes that digest lactose. Tap the lactose and glucose supplies (or use the checkboxes) and watch the repressor let go, the CAP activator dock, and RNA polymerase start transcribing. The graph shows the enzyme level climbing or decaying in response.
Labs / Biology / Gene Switch (Lac Operon)
Gene Switch (Lac Operon)
This is how a bacterium decides whether to make the enzymes that digest lactose. Tap the lactose and glucose supplies (or use the checkboxes) and watch the repressor let go, the CAP activator dock, and RNA polymerase start transcribing. The graph shows the enzyme level climbing or decaying in response.
Why it matters
Why explore this?
Living systems are connected and constantly changing. This model makes one biological process visible so you can test how its parts affect one another.
Explore
Try the model
Promoter ActiveTranscription 0%Enzyme 0%
Investigate
Questions to test
Predict first, try it in the model, then use what you observe to answer.
What to try
- With no lactose around, what is the repressor doing to the operator — and can RNA polymerase get through?
- Add lactose but keep glucose present. Why does transcription only trickle instead of running full speed?
- Now remove the glucose. What docks onto the CAP site, and how fast does the enzyme level shoot up?
- Switch lactose off after the enzyme is high. How long does the enzyme linger before it decays away?
- Slide the enzyme decay rate up and down — does it change the final steady level, the speed of the response, or both?
Explain
Make sense of what happened
Explain the process as a chain: a change happens, the system responds, and that response affects what happens next. Use an observation from the model as evidence.
Check
Before you leave
How did the system respond?
How would you explain that response?
If you can answer all three using evidence from the model, you understand the main idea. If not, return to Explore and change one setting at a time.