Fig. 1. Construction and characterization of Ar conditional allele. (A) Schematic of targeting construct (pyARdt1), wild-type and conditional hypomorphic (Ar^{flox(ex1-neo)}) alleles of Ar. Arrows over loxP sites indicate orientation of sites relative to one another. Probe used for Southern blots is indicated above exon 1. (B) EcoRV digest and Southern blot of ES cell DNAs. Probe detects presence of 12.5kb Ar fragment in wild-type FWB2 ES cells. Correctly targeted ES cell clones Ar126 and Ar206 contain only the 9 kb fragment representative of the correctly targeted allele. (C) Chimeric males transmit the X-linked Ar^{flox(ex1-neo)} allele exclusively to female offspring. (D) PCR genotyping detects the Ar inversion allele, inv(ex1-neo), specifically in the testes of Ar^{flox(ex1-neo)/Y}; Amh-cre animals. No product is observed in tails from the same animals or in testes or tails from Ar^{flox(ex1-neo)/Y} males. The non-recombinant hypomorphic allele, flox(ex1-neo), is detected in all samples. Te, testis; Ta, tail.