The LbCas12a entry in FlyBase represents a RNA-guided nuclease which is derived from the naturally occurring Cas12a endonuclease from Lachnospiraceae bacterium. The exact sequence of the nuclease may differ depending on the particular transgene or modified endogenous locus being used, for example, the coding sequence may have been codon optimized for use in different species. For gene targeting, LbCas12a nuclease requires a short CRISPR RNA (crRNA) that contains nucleotides complementary to the genomic target site of interest, plus additional sequence required for LbCas12a protein binding, with complementary sequence of length of 21-23 nucleotides resulting in the highest level of genome modification. Provided that a 4 nucleotide protospacer adjacent motif (PAM) sequence (TTTV) is present at the target site immediately 5' to the sequence targeted by the crRNA, then cleavage at the genomic target site can occur. Cleavage mediated by LbCas12a results in a staggered double-strand break (PMID:26422227, PMID:29843790). LbCas12a also has an RNase activity that enables it to process single cRNAs from a precursor CRISPR repeat array (PMID:27918548).