Marker-assisted selection produced congenic NZB Lck-cre and NZW.ERαfl/fl mice at the N6 backcross generation. Both NZB.Lck-cre (a) and NZW.ERαfl/fl (b) mice were genotyped via SNPs using the DartMouse Speed Congenic Core Facility. The genomic regions containing the Lck-cre transgene in NZB mice and the floxed ERα allele in NZW mice are indicated by boxes. In a subset of the N6 mice genotyped from each congenic strain, several individual SNPs (indicated as grey boxes with black borders) on different chromosomes were called as heterozygous (NZB/FVB or NZW/B6, respectively). However, in the N5 congenic parent and the N4 congenic grandparent of these N6 congenic mice, these same SNPs were genotyped as homozygous (NZB/NZB or NZW/NZW, respectively). Thus, we conclude that the designations of these N6 congenic mice as heterozygous at these few SNPs represent miscalls.