The transgene insert comprises the following elements: the CAG promoter, a loxP site, the EGFP fluorescent reporter gene, poly(A) signal sequence, a loxP site, the mCherry fluorescent reporter gene, sequence coding for T2A self-cleaving peptide, the cDNA sequence for the mouse Dnmt3a2 short splice variant, sequence coding for T2A self-cleaving peptide, mouse Dnmt3l cDNA sequence, and poly(A) signal sequence. This allele expresses the EGFP gene; mCherry, Dnmt3a and Dnmt3l are only expressed after cre-mediated recombination removes the EGFP gene. (J:210999)