In some embodiments, aspects of the disclosure provide methods and compositions that are useful for modifying (e.g., mutating) one or more alleles of a genomic locus within a cell. In some embodiments, methods and compositions described herein involve producing a chimeric spliced RNA molecule that includes a transcribed exon spliced to a nuclease interacting RNA segment. In some embodiments, the chimeric spliced RNA guides a DNA modifying enzyme (e.g., a nuclease) to a genomic locus in a cell, thus achieving modification of the locus.