The context-sensitive HMM proposed to represent miRNA precursors with estimated transition probabilities. State P1 emits the upper halves of the stem and symmetric bulges. States S1 and S3 emit the asymmetric bulges in the upper and lower sections respectively. State S2 emits the loop. States C11 and C12 emit the lower halves of the stem and symmetric bulges respectively (~ refers to probabilities averaged over the four possible top-of-stack symbols).