Variation of cats under domestication: genetic assignment of domestic cats to breeds and worldwide random-bred populations.

Both cat breeders and the lay public have interests in the origins of their pets, not only in the genetic identity of the purebred individuals, but also in the historical origins of common household cats. The cat fancy is a relatively new institution with over 85% of its 40-50 breeds arising only in the past 75 years, primarily through selection on single-gene aesthetic traits. The short, yet intense cat breed history poses a significant challenge to the development of a genetic marker-based breed identification strategy. Using different breed assignment strategies and methods, 477 cats representing 29 fancy breeds were analysed with 38 short tandem repeats, 148 intergenic and five phenotypic single nucleotide polymorphisms. Results suggest the frequentist method of Paetkau (single nucleotide polymorphisms = 0.78, short tandem repeats = 0.88) surpasses the Bayesian method of Rannala and Mountain (single nucleotide polymorphisms = 0.56, short tandem repeats = 0.83) for accurate assignment of individuals to the correct breed. Additionally, a post-assignment verification step with the five phenotypic single nucleotide polymorphisms accurately identified between 0.31 and 0.58 of the misassigned individuals raising the sensitivity of assignment with the frequentist method to 0.89 and 0.92 for single nucleotide polymorphisms and short tandem repeats respectively. This study provides a novel multistep assignment strategy and suggests that, despite their short breed history and breed family groupings, a majority of cats can be assigned to their proper breed or population of origin, that is, race.

A case of SRY-positive 38,XY true hermaphroditism (XY sex reversal) in a cat.

Investigation of abnormal sexual development in companion animals can allow for the elimination of inherited disorders from breeding populations while contributing to the understanding of the complex process of mammalian sexual development and differentiation. A 1-year-old mixed-breed cat, presented for neutering, was tentatively diagnosed as a male with bilateral cryptorchidism. During surgery, the surgeon identified gonads in an ovarian position and a complete bicornuate uterus. Both testicular and ovarian architecture in the gonads and Mullerian and Wolffian duct derivatives were identified histologically. The karyotype was that of a normal male (38,XY), and no causative mutation was identified in the feline SRY coding sequence amplified from genomic DNA. All features of the case were compatible with a diagnosis of SRY-positive 38,XY sex reversal, true hermaphrodite phenotype. To the authors' knowledge, this is the first report of this disorder in a domestic cat.

The Tabby cat locus maps to feline chromosome B1.

The Tabby markings of the domestic cat are unique coat patterns for which no causative candidate gene has been inferred from other mammals. In this study, a genome scan was performed on a large pedigree of cats that segregated for Tabby coat markings, specifically for the Abyssinian (Ta-) and blotched (tbtb) phenotypes. There was linkage between the Tabby locus and eight markers on cat chromosome B1. The most significant linkage was between marker FCA700 and Tabby (Z = 7.56, theta = 0.03). Two additional markers in the region supported linkage, although not with significant LOD scores. Pairwise analysis of the markers supported the published genetic map of the cat, although additional meioses are required to refine the region. The linked markers cover a 17-cM region and flank an evolutionary breakpoint, suggesting that the Tabby gene has a homologue on either human chromosome 4 or 8. Alternatively, Tabby could be a unique locus in cats.

Origins of primate chromosomes - as delineated by Zoo-FISH and alignments of human and mouse draft genome sequences.

This review examines recent advances in comparative eutherian cytogenetics, including Zoo-FISH data from 30 non-primate species. These data provide insights into the nature of karyotype evolution and enable the confident reconstruction of ancestral primate and boreo-eutherian karyotypes with diploid chromosome numbers of 48 and 46 chromosomes, respectively. Nine human autosomes (1, 5, 6, 9, 11, 13, 17, 18, and 20) represent the syntenies of ancestral boreo-eutherian chromosomes and have been conserved for about 95 million years. The average rate of chromosomal exchanges in eutherian evolution is estimated to about 1.9 rearrangements per 10 million years (involving 3.4 chromosome breaks). The integrated analysis of Zoo-FISH data and alignments of human and mouse draft genome sequences allow the identification of breakpoints involved in primate evolution. Thus, the boundaries of ancestral eutherian conserved segments can be delineated precisely. The mapping of rearrangements onto the phylogenetic tree visualizes landmark chromosome rearrangements, which might have been involved in cladogenesis in eutherian evolution.