Figure 1.

Tags were synthesized by eight rounds of combinatorial synthesis, wherein each word, w₁–w₈, is added in a separate column of a DNA synthesizer. In each round, a word was added to each growing tag by four conventional base-coupling cycles, after which the microbeads were mixed and divided for the next addition. After the eighth round, a portion of the microbeads were separated for further synthesis of a 5′ primer-binding site (PBS), followed by cleavage, amplification, and insertion into pLCV1.