Fig. 1. MicroRNAs control developmental timing. (A) C. elegans cell lineage diagram for the seam cells V1-V4 and V6. Developmental time is the vertical axis. 1 to 4, larval stages L1 to L4; A, adult stages. Colours refer to developmental stage. H, cell fused to hypodermis. Triple black line, terminal differentiation signified by lateral alae. Dotted lines, continued cell division according to the same pattern. (B) Simplified genetic pathway of the heterochronic genes in C. elegans. Dashed line represents possible late role for mir-48, mir-84 and mir-241 during development.