Programmable guide RNAs (gRNAs) play a central role in the CRISPR revolution sweeping biology and medicine by directing the function of a Cas protein effector to a target gene of choice. To achieve programmable control over regulatory scope, the activity of a conditional guide RNA (cgRNA) depends on the presence or absence of an RNA trigger, allowing for cell-selective regulation of CRISPR/Cas function. Unlike a standard gRNA, a cgRNA is programmable at multiple levels, with the target-binding sequence controlling the target of Cas activity (edit, silence, induce, or bind a gene of choice) and the trigger binding sequence controlling the scope of Cas activity. cgRNA mechanisms that are allosteric allow for independent design of the target and trigger sequences, providing the flexibility to select the regulatory target and scope independently. Disclosed herein are allosteric cgRNA mechanisms for both ON→OFF logic (conditional inactivation by an RNA trigger) and OFF→ON logic (conditional activation by an RNA trigger). Allosteric cgRNAs enable restriction of CRISPR/Cas function to a desired cell type, tissue, organ, or disease state. Allosteric cgRNAs provide a versatile platform for cell-selective and tissue-selective research tools, biotechnologies, diagnostics, and therapeutics.