The invention provides a nucleic acid comprising a Cpf1 crRNA, a processing sequence 5' of the Cpf1 crRNA, and an extension sequence 5' of the processing sequence. The invention also provides a composition comprising the nucleic acid, a carrier, and optionally Cpf1. Additionally, the invention provides method of genetically modifying a eukaryotic target cell, comprising contacting the eukaryotic target cell with the nucleic acid or the composition to genetically modify a target nucleic acid in the cell.
