Genetic circuits
flickr - Gaetan Lee
The study of genetic circuits is an increasingly acknowledged bioengineering discipline, it is mainly about genetically engineered cells with genes impacting each other’s gene expressions. Similar to the concepts of electronic parts working as a system, as a genetic regulatory network, they perform tasks such as digital computation and signal processing. It will allow organisms with engineered genetic networks to perform novel biological functions which are not possible or difficult to achieve with System Biology, such as in vivo computing, biosensing, or even detecting specific abnormal behaviours in the environment and response accordingly.
To construct sophisticated genetic networks, those which are analogous to integrated circuits, we need to begin with smaller building blocks. Therefore, the current phase of development, like the early stage evolution of modern electronics in the twentieth century, is to construct a genetic library of these building blocks similar to circuit components such as analogue amplifiers and digital logic gates.
Let us consider a simple electronic NOT gate, or an inverter, if it has an input of a voltage higher than a preset threshold, its output will switch to a low voltage in response and vice versa. Similarly, if we need to construct a biochemical inverter embedded in the genes of E. coli, then we may engineer it in a way that the input signal, which is the concentration of input mRNA, determines the output... (Read more)
In a digital circuit, we always have a propagation delay between the input and output, this is also true for a genetic circuit. A ring oscillator, which is a device assembled with an odd number of inverters attached in a series, and the final output from the last inverter is fed back to the input of the first inverter, can be constructed using this characteristic... (Read more)
With the genes we proposed for development in cells, it is likely that we end up with a genetic circuit which is not working for what we intended, or even non-operational. Even in the case of a simple inverter, some characteristics we designed for the circuit are difficult to be ensured. This inverter may simply be not working for any input levels, or working but in undesired levels... (Read more)