Mi{24xMS2-V6} represents a transgenic construct generated in vivo by using phiC31:int-mediated recombination to replace the attP cassette of a Mi{MIC} element insertion with a '24xMS2-V6' stem-loop cassette that contains 24 copies of Tag:MS2 (the cassette contains 2 tandem copies of a sequence encoding 12 unique Tag:MS2 stem loops). Each copy of Tag:MS2 contains a U instead of C at a crucial nucleotide in the Tag:MCP binding site that weakens the interaction and makes the Tag:MS2-Tag:MCP interaction less stable. Insertion of the Mi{24xMS2-V6} cassette in the correct orientation into an intron of a gene of interest allows visualization of nascent transcription of that gene; the Tag:MS2 sequences in the nascent transcript form stem loops that can be detected by a reporter protein that includes Tag:MCP (which binds Tag:MS2).