From 2007.igem.org

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Contents 1 Bacterial counter 1.1 Project Goal 1.2 Current Device Idea 1.3 Assumptions 1.4 Initial Experiments

Bacterial counter

The idea is to use a variety of recombinases to delete or invert sections of DNA and use this to count or trigger the expression of genes.

Project Goal

The aim is to produce output as a function of cell division. This can have the added potential of performing programmed cell death after a determined number of cell divisions. We also hope to further analyse cell division and recombinase mechanisms.

Current Device Idea

This device should output a PoPS signal every time a cell division occurs This can then be hooked up to another device such as a counter.

This device realise on dif sites flipping only once per division. In it's current configuration, Promoter A is repressed by represser A which is continually being produced. at this time there is no represser B being produced.

When cell division occurs, the section of DNA between the two dif sites gets reversed. Initially there is no represser B present in the cell so promoter B is able to produce an output of PoPS. As time goes on represser B gets produced and 'turns off' promoter B. At the same time represser A is no longer being produced and degrades (?) so when the next division occurs, promoter A will be capable of producing a PoPS output and the process repeats.

Assumptions

• The Dif sites flip only once during cell division
• Repressors A and B are produced and degrade faster than the cell cycle
• Promoter B does not interfere with the production of represser A

Initial Experiments

To test whether this actually happens or not we will build this smaller, simpler device to prove flipping occurs upon cell division and a second test to show whether it flips once or many times per division