Synthetic Counter (iGem2005 ETH Zurich)
From 2006.igem.org
Abstract. We report here the design and implementation in vivo of a gene circuit that can count up to 4. In essence, it uses two toggle switches, each storing 1 bit, to keep track of the 4 states. The design of the counter is highly modular, with the hope that it can be included as a unit in larger circuits, and also combined with further counter instances to keep track of a much larger number of states, up to (2^(n+1)) with n units. To facilitate further developments and integration to other projects, the counter is available in form of BioBricks. Among many exciting applications, the availability of a counter enables the execution of sequential instructions, and paves the way for the execution of artifical programs inside living cells.
Contents |
Introduction
The past few years have seen the emergence of the field of synthetic biology, in which functional units are designed and built into cells to generate a particular behaviour, and ultimately to better understand Life's mechanisms. Previous efforts include the creation of gene circuits that generate oscillating behaviour (Elowitz00), toggle switch functionality (Atkinson03), artificial cell-cell communication (Bulter04) or pattern-forming behaviour (Basu2005). The present document describes the design and realization of a gene circuit that counts to 4.
Design of the Counter
In summary, the counter uses an input signal to switch from one of the four output to the next. When the input signal is high, either output 1 or 3 is active, when it is low, output 2 or 4 is active. Thus output 1 and 3 alternatively keep track of high input signal, while output 2 and 4 alternatively keep track of low input signals.
As depicted above, the counter is made of two parts, serially linked:
- the "Input" module, which splits the input into two opposite signals.
- the "NOR" module, which sequencially switches through the outputs 1, 2, 3 and 4.
Note that the concepts behind the metric all interfaces, Polymerase Per Second (PoPS), is explained in details on the ([http://partsregistry.org/cgi/htdocs/AbstractionHierarchy/index.cgi abstraction hierarchy] of the MIT Registry of Parts.
