Figure 3.

A perfect library generated by random priming should contain a complete set of genomic inserts starting (and ending) at each nucleotide of the genome. The diagram above shows a hypothetical set of library fragments with genomic inserts 36 bases long and a hypothetical binding site of 26 bases. These and only these fragments will survive to the final round of SELEX. The primer sequences (underlined) allow PCR amplification, while the T7 promoter (indicated with asterisks) is used when RNA is the target.