Report on rat chromosome Y

Experimental Animal Science

R e p o r t on rat c h r o m o s o m e Y MONTE E. TURNER University of Akron, Akron, USA

Introduction At least five loci have been identified on the rat Y chromosome and three additional phenotypes, for which specific loci have not been identified, have been mapped to the rat Y chromosome (Table 1). The five specific loci are genes that are conserved on many mammalian Y chromosomes and most have been identified and/or isolated using this homology. All loci identified to date are located in the nonrecombining portion of the rat Y chromosome and no genes have been localized with respect to any other locus.

Genes The Sry locus needs particular discussion because the organization in the rat is different from either the human or laboratory mouse Y chromosome. The Sry locus has been confinned with transgenic experiments to be the testis determining locus (Tdy/TDF)(1). In fact in the mouse/human genome databases Sry has been renamed Tdy/TDFand Sry withdrawn. At this time in the rat we prefer not to do that because the rat contains 3-5 copies of the Sry locus (2) and the function or organization of these repeated loci is not known. Until these loci are examined in detail and differentiated we propose continuing the Sry designation with numerical additions (Sry-1, Sry-2 etc.) as individual copies are identified. Once differentiated, expression studies can be used to confirm which copy or copies function as Tdy. The phenotypes mapped to the rat X chromosome have been given symbols as indicated in table 1. The Hy locus, the male histocompatability locus, and the Smcy locus are probably the same locus identified or mapped in two different ways (3). The Hy was mapped and identified from phenotypic data and Smcy identified from molecular similarity to mouse and human Smcy/SMCY.The mouse and human databases continue to recognize both as separate loci at this time and we have followed that designation. J. Exp. Anita. Sci. 1999; 40:161-162 Urban & Fischer Verlag http://www'urbanfischer'de/j°urnals/jeansc 0939-8600/99/40/01-03-161 $12.00/0

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