  Biomolecular computers, along with quantum computers, may be a future
alternative for traditional, silicon-based computers. Main advantages of
biomolecular computers are massive parallel processing of data, expanded
capacity of storing information and compatibility with living organisms (first
attempts of using biomolecular computers in cancer therapy through blocking of
improper genetic information are described in Benenson et al.(2004). However,
biomolecular computers have several drawbacks including time-consuming
procedures of preparing of input, problems in detecting output signals and
interference with by-products. Due to these obstacles, there are few laboratory
implementations of theoretically designed DNA computers (like the Turing
machine and pushdown automaton), but there are many implementations of DNA
computers for particular problems. The first practical laboratory
implementation of the general theoretical model of a machine performing
DNA-based calculations was a simple two-symbol two-state finite automaton
established by Benenson et al.(2001). In the present work, we propose a new
attitude, extending the capability of DNA-based finite automaton, by employing
two or potentially more restriction enzymes instead of one used in other works.
This creates an opportunity to implement in laboratories of more complex finite
automata and other theoretical models of computers: pushdown automata, Turing
machines.
