The cDNA for a modified DsRed fluorescent protein (designated as tdTomato) along with a synthetic bovine growth hormone polyadenylation signal was inserted into the Drd1a BAC clone RP23-47M2 by homologous recombination in E coli. The tdTomato cDNA replaced the ATG codon as well as an additional 180 bp of coding sequence. Six independent founder lines were established but only line 5 has been reported.