Table 5.

Comparison of general properties between miRNA and siRNA

Nucleic acids	Occurrence	Configuration/length	Complementarity to target mRNA	Action	Function	Clinical uses
miRNA	Plants and animals	Single stranded/19–25 nt	Not exactly a perfect match, only at seed level; a single miRNA may target up to hundreds of mRNAs	Inhibit translation of mRNA	Modulators of gene expression regulation	Used as drug targets or biomarkers and diagnostic tools186,189
siRNA	Plants and lower animals	Double stranded/21–22 nt	Perfect match, siRNAs knock down specific genes, with minor off-target exceptions	Cleavage of mRNA	Act as gene-silencing guardians	Used to knock down specific genes, with application in clinical trials as therapeutic agents186,189

Abbreviations: miRNA, microRNA; siRNA, small interfering RNA; nt, nucleotides.