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.

Tyrosinase mutations associated with Siamese and Burmese patterns in the domestic cat (Felis catus).

The Siamese cat has a highly recognized coat colour phenotype that expresses pigment at the extremities of the body, such as the ears, tail and paws. This temperature-sensitive colouration causes a 'mask' on the face and the phenotype is commonly referred to as 'pointed'. Burmese is an allelic variant that is less temperature-sensitive, producing more pigment throughout the torso than Siamese. Tyrosinase (TYR) mutations have been suspected to cause these phenotypes because mutations in TYR are associated with similar phenotypes in other species. Linkage and synteny mapping in the cat has indirectly supported TYR as the causative gene for these feline phenotypes. TYR mutations associated with Siamese and Burmese phenotypes are described herein. Over 200 cats were analysed, representing 12 breeds as well as randomly bred cats. The SNP associated with the Siamese phenotype is an exon 2 G > A transition changing glycine to arginine (G302R). The SNP associated with the Burmese phenotype is an exon 1 G > T transversion changing glycine to tryptophan (G227W). The G302R mutation segregated concordantly within a pedigree of Himalayan (pointed) Persians. All cats that had 'pointed' or the Burmese coat colour phenotype were homozygous for the corresponding mutations, respectively, suggesting that these phenotypes are a result of the identified mutations or unidentified mutations that are in linkage disequilibrium. Because the same mutations were identified in different breeds with similar phenotypes, the mutations are likely to be identical by descent rather than multiple mutation events occurring at the same site.

Serosurvey of selected zoonotic agents in polar bears (Ursus maritimus).

Between 1982 and 1999 blood samples were collected from 500 polar bears (Ursus maritimus) captured in the Beaufort and Chukchi seas, to determine the seroprevalence of Brucella species, Toxoplasma gondii, and Trichinella species infections. The bears were classified into four age groups, cubs, yearlings, subadults and adults. Brucella and Toxoplasma antibodies were detected by agglutination (a buffered acidified card antigen and rapid automated presumptive test for brucellosis and a commercial latex agglutination test for toxoplasmosis); an ELISA was used to detect Trichinella antibodies. The overall seroprevalence of Brucella species was 5 per cent, and subadults and yearlings were 2-62 times (95 per cent confidence interval 1.02 to 6.82) more likely to be seropositive for Brucella species than adults and their cubs. The antibody prevalence for Toxoplasma gondii was 6 per cent, and for Trichinella species 55.6 per cent. The prevalence of antibodies to Trichinella species increased with age (P<0.001).