The cluster containing Mir449a, Mir449b and Mir449c was flanked by loxP sites. The cluster Mir449 is embedded into intron 2 of the predicted mouse gene Cdc20b (ENSMUSG00000078926). Mir449c is located 206 bp downstream of the predicted exon 2 of the Cdc20b gene. The proximal LoxP site was inserted within these 206 bp. Recombination removed the selection cassette and microRNA cluster. (J:147112)