For the past few years scientists have been creating genetic Boolean logic circuits in the field called synthetic biology. The genetic ON and OFF switches would create the simple logic functions. This is being done by altering the connection between genetic components and building new regulatory networks to mimic the behaviour of the logic gates like NAND/NOR or NOT gates.
Bacteria like E. coli have been employed as living Boolean logic gates and in future they can serve as the potential building blocks for bio-computer.
Scientist have created the AND gate within a bacterial host using two promotor inputs. When both inputs are there then they generate a pair of co-activating genes which compel the production of two precise proteins that interact with one another to bring about a third gene which brings the output of the circuit.
Actually these genetic circuits are the main theme of the current system biology but it lacks the same inevitability and trustworthiness as seen in other full-grown engineering fields.
Following these gates we can use these living cells in programming to generate definite and desired results in reply of particular intra or extra-cellular signalling inputs. If we are able to connect enough if these type of circuits or gates; that day is not so far to have a living or Bio-Computer.