ELSEVIER SRY-NEGATIVE XX TRUE HERMAPHRODITE IN A BASSET HOUND M. Hubler,l B. Hauser,* V.N. Meyers-Wallen, and S. Arnold1 Departments of lReproduction, and *Pathology, University of Zurich Zurich, Switzerland 3 Department of Clinical Sciences, New York State College of Veterinary Medicine Cornell University, Ithaca, NY, USA 14853-6401 Recieved for publication: November 3, 1998 Accepted: January 22, 1999 ABSTRACT A true hermaphrodite was diagnosed in a 7-mo-old Basset hound. The diagnosis was based on the clinical signs, the histology of the gonads and the karyogram. Additionally, the dog was tested for the Y-linked gene Sry, which was negative. The Basset hound presented here is compared to other XX sex reversed animals described in the literature. In man, XX sex reversal is a heterogenous condition. The pathogenesis in Sry-negative individuals is not understood. Thus Q-y-negative animals could serve as an animal model of the human disease. 0 1999 by Elsevier Science Inc. Key words: true hermaphrodite, Q-y-negative, Basset hound INTRODUCTION Normal sexual differentiation of the embryo is dependant upon the completion of 3 major events (9,16). It begins with the establishment of the chromosomal constitution of the zygote as XX or XY at fertilization. The chromosomal sex then determines gonadal sexual differentiation. The development of the testis is initiated by the Sry gene, which is normally located on the Y chromosome. Expression of the Sry gene in the testis occurs only during a short period in the embryonic development (7). In the absence of a Y chromosome, ovarian differentiation normally occurs. The final step in establishing the phenotypic sex is regulated by the gonads after differentiation. In the early embryo, the genital system is sexually undifferentiated. At this stage, both XX and XY Theriogenology 51:1391-1403, i999 0093~691XB9B-we frunt matter Q 1999 by Elsevier Science Inc. PII SOO93-691X(99)00082-5