In the near future, biological circuits will be much more modular and sophisticated than they are now, with a ten-fold smaller nucleotide footprint.
The Enabling Technology: Toehold-Mediated Strand Displacement
A gate strand and output strand exist as a complex that is partially bound through complementary Watson-Crick base-pairing within the S2 binding domain. The gate strand also contains an open, unbound domain called a toehold region, T*. An input strand with a free complementary toehold region, T, can bind to the toehold region on the gate strand, and subsequently displace the output strand to yield an input-gate complex. This is called a toehold-mediated strand displacement reaction. The output strand is used as an input for a downstream gate-output complex.
Background
Qian and Winfree (Science 2011) utilized DNA computation to create AND and OR logic gates in vitro. They constructed a sophisticated binary square root circuit using these gates:
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