A set of transgenic constructs that each contain UAS regulatory sequences driving expression of two different sgRNAs, both of which target common coding exons within the 5' half of a single gene of interest without overlapping the start codon; this is designed to result in an indel (small insertion or deletion mutation) of the target gene in the presence of a source of Cas9. Designed for conditional CRISPR/Cas9 mutagenesis; a GAL4 driver can be used to express a HD_CFD construct and a UAS-Cas9 transgene in a tissue-specific manner, inducing mutagenesis only in the GAL4-expressing cells.