Figure 1.

Unexpected offspring genotype ratio during the breeding of Foxp3^YFP‐Cre to Insr^fl/fl mice. (a) Breeding scheme to generate Foxp3^YFP‐CreInsr^fl/fl mice and Foxp3^YFP‐CreInsr^fl/wt littermate controls, with expected genotype ratios. Circles represent females, squares represent males, and diamonds represent mice of either sex; shading indicates the expected number of Insr^fl alleles. The dashed line indicates progeny in the F₄‐generation with an unexpected genotype. (b) Depiction of the conventional two‐band genotyping PCR strategy, in which primers flanking the loxP site that is 3′ of Insr exon 4 amplify different PCR products depending on the presence of a floxed or a wild‐type allele (top). Representative PCR products are resolved on a 2% agarose gel, with each lane representing one mouse (bottom). (c) Punnett square showing the expected F₄‐generation genotype ratio from Foxp3^YFP‐CreInsr^fl/fl mice and Foxp3^YFP‐CreInsr^fl/wt parents (left). Table compares expected and actual F₃ offspring ratios (right). n = 62 in the F₄ generation.