1 | Always endogenous | Can be endogenous or exogenous |
2 | Usually derived from genomic loci distinct from recognised genes | Usually derived from mRNAs, transposons, viruses or heterochromatic DNA |
3 | Formed from local RNA hairpin structures | Produced from long exogenous or endogenous dsRNA molecules (very long hairpins or bio-molecular duplexes) |
4 | A single miRNA:miRNA* duplex is generated from each hairpin precursor | Multiple duplexes are generated |
5 | Highly conserved among species | Rarely conserved |
6 | Hetero-silencing; ie, target remote loci | Auto-silencing; ie, target the same locus |
7 | Processed in the nucleus by Drosha and in the cytoplasm by dicer | Processed in the cytoplasm by dicer |
8 | Perform function by either suppressing protein synthesis or mRNA cleavage | Perform function by mRNA cleavage |