This invention provides UNA oligomers for therapeutics that can be used to modulate or reduce gene expression. The UNA oligomers can be composed of one or more 2′-3′-seco-nucleomonomers and one or more natural or non-natural nucleotide monomers, and can be a duplex having first and second strands. Embodiments include UNA oligomers with phosphorothioate or boranophosphate intermonomer linkages. The UNA oligomers can provide reduced off target effects while modulating gene expression.