Fig. 4: DNA for identification and computing applications.

a Applications of DNA barcoding. Applications include product tagging and DNA of things, as discussed in this review, but also species identification, cancer cell detection, or unique molecular identifiers, which lie outside of the scope of this review. b AND logic gate and truth table. DNA logic gates with input signal strands «A» and «B» and output signal strand «X». Toehold regions are marked in orange and yellow, signal strands are marked with capital letters and complementary strands are marked with lower case letters. Signal strands are dark blue whereas all other strands are gray. Input signal A binds to gate complex (containing strands a, b, and X) and displaces a part of strand b to form “waste” complex A-a. Input signal B is then added. It displaces output signal X from the complex to bind with b, forming “waste” complex B-b. Single strand X is the output signal of the gate.