Model of CRISPR transcript processing. The unprocessed transcripts (pre-crRNAs) are generated with rate ϕ, and are consequently either (non-specifically) degraded with rate λ
, or processed to crRNAs by CasE with rate k. crRNAs are then degraded with rate λ
. Concentrations of pre-crRNAs (unprocessed transcripts) and crRNAs (processed transcripts) are denoted as, respectively, [u] and [p].