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Cytogenetic and histologic studies of tortoiseshell cats

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Cytogenetic and histologic studies of tortoiseshell cats

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Abstract

The tortoiseshell coat colour of the domestic cat is produced by the epistatic effect of the Sex-linked orange gene (O) on the autosomal black or tabby genes, In cells with an Q gene on the X chromosome, the fur will be L Orange (ginger), even if there are black or tabby genes on the autosomes. Therefore male cats can be either (XY)-Y-O ginger toms, or X-Y black or tabby toms, depending upon which autosomal genes are present. Females with two X chromosomes have three possibilities: X-X- cats will be black or tabby females: depending upon which autosomal genes are present; (XXO)-X-O animals will be ginger females, and (X-XO) Cats will be tortoiseshell females. The variegated pattern of the tortoiseshell coat colour is produced by the random inactivation of one of the X chromosomes in each XX cell, which in the cat occurs on about the 12th day of embryogenesis. In theory, male tortoiseshell cats should not occur, because normal males do not have two X chromosomes, and thus the two coat colours (orange and non-orange) cannot occur in the same: animal. Nevertheless, many male tortoiseshell cats have been reported and most have been found to have an abnormal chromosome complement. In this article the chromosome complement and histological analysis of tortoiseshell males in the studied cat population of the United Kingdom and USA have been described. With an estimated 7.2 milion cats in the UK, and a prevalence of 0.43 % of tortoiseshell male cats being chromosomally abnormal(in the USA - 0.033%), approximately 14 700 cats could possess a chromosome complement of (XY)-Y-O/X-Y, XX/XY or XXY.

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... A number of studies have attempted to study the genetic basis of tortoiseshell coats in male domestic cats. As the orange locus in the cat is X-linked(Grahn et al., 2005), the most frequently expected cause of this phenotype is the presence of an extra X chromosome in the form of a trisomy XXY, mosaic variants XY/XXY or XY/XYY and also XX/XY chimerism(Balogh et al., 2015;Kosowska, Januszewski, Tokarska, Jach, & Zdrojewicz, 2001;Meyers-Wallen, 2012;Szczerbal et al., 2018). Therefore, the expected side effect of such a coat is infertility associated with reproductive disorders. ...
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The tortoiseshell coat colour is characteristic to female cats and its occurrence in tomcats is very rare and associated with chromosome abnormalities (additional copy of X chromosome). The aim of this study was identification of the genetic basis of a case of tortoiseshell color in a fertile Maine coon tomcat. Cytogenetic and molecular genetic studies were carried out with painting molecular probes (WCPP) specific to the X and Y sex chromosomes as well as a DNA microsatellite panel for the parentage verification of cats. Cytogenetic analysis revealed only a single set of sex chromosomes typical for male ‐ 38,XY. The results of the microsatellite polymorphism obtained from DNA showed three alleles in locus FCA201 and four alleles in loci FCA149 and FCA441 in different tissues (blood, hair roots and testicles). Based on these results the case was diagnosed as a true chimerism 38,XY/38,XY. To the best of our knowledge this is the first case of a 38,XY/38,XY chimera diagnosed in cats, confirmed by genetic analysis.
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... Females heterozygous for the orange locus have a brindled black and orange coat colour that is commonly termed tortoiseshell. Tortoiseshell males have occurred but are usually infertile and have been shown to be chimeras (XY/XXY) or trisomies for the sex chromosomes, generally presenting as XXY (Chu et al. 1964;Gregson & Ishmael 1971;Kosowska et al. 2001). ...
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