 dynamic 
 rna nanotechnology based on programmable hybridization 
 cascades with small conditional rnas ( scrnas ) offers a promising conceptual 
 framework for engineering programmable conditional regulation in vivo . 
 
 while single - base substitution ( sbs ) somatic mutations and single - nucleotide 
 polymorphisms ( snps ) are important markers and drivers of disease , 
 it is unclear whether synthetic rna signal transducers are sufficiently 
 programmable to accept a cognate rna input while rejecting single - nucleotide 
 sequence variants . here 
 , we explore the limits of scrna programmability , 
 demonstrating isothermal , enzyme - free genotyping of rna sbs cancer 
 markers and snps using scrnas that execute a conditional hybridization 
 cascade in the presence of a cognate rna target . 
 kinetic discrimination 
 can be engineered on a time scale of choice from minutes to days . 
 to discriminate even the most challenging single - nucleotide sequence 
 variants , including those that lead to nearly isoenergetic rna wobble 
 pairs , competitive inhibition with an unstructured scavenger strand 
 or with other scrnas provides a simple and effective principle for 
 achieving exquisite sequence selectivity . 
Supplementary Material