 Genetic testing for the coat colours
chocolate and cinnamon and coat variants Burmese and Siamese
| Siamese and Burmese patterns | | | | The Siamese pattern is reponsible for a phenotype representing a mild form of albinism. This temperature-sensitive mutation produces normal colour pigment only at the cooler extremities of the body, causing a ”mask” of the face as well as darkened paws and tail. The Siamese pattern is also called mask factor or point, since normal pigmentation occurs only at the cooler points of the body.
The Burmese pattern, the mildest form of albinism, is characterized by a normal pigmentation of the extremities and a slight shading of normal body colour.
Two mutations in the gene encoding the enzyme tyrosinase which is required for melanin production are responsible for these colour variants. This gene locus is called C-locus. The wild type allele C is dominant and causes full pigmentation, the Siamese cs allele is recessive and leads to the characteristic distribution of the dark colour on ears, mask, tail and legs when in the homozygous state. The Burmese pattern also follows a recessive inheritance and leads to the coat colour Burmese brown in the homozygous state, with varying degrees of black and dark brown.
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| Chocolate and cinnamon coat colours | | | | The coat colours chocolate and cinnamon are caused by mutations in the gene TYRP1 (tyrosinase-related protein 1) which is involved in the production of the black colour pigment eumelanin. This gene locus is called B-locus. The brown variants show a suggested allelic series, with the following dominance pattern: B > b > b1. The B allele is dominant and represents the normal “wild type” black coat colour. Cats with “brown” genotypes bb or bb1 have a chocolate phenotype, whereas cats with the “light brown” genotype b1b1 have a cinnamon phenotype, independent of B and b alleles.
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| How can the different genotypes for the colours chocolate and cinnamon and the Siamese and Burmese patterns be identified ? | | | | Recently, the mutations leading to the different coat colours have been found in the USA, thus permitting the development of a genetic test for each of the colours. After validating these tests in collaboration with several german veterinarians and cat breeders, Laboklin GmbH & Co.KG in Bad Kissingen can now offer the tests to all interested breeders. For the coat colour chocolate, Laboklin tests the four most important gene loci, therefore ensuring a very reliable test. For the coat colour cinnamon as well as the Siamese and Burmese coat patterns, only one mutation has been published to be responsible for the corresponding colour.
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| How does the genetic test work and how safe is it? | | | | Firstly, the DNA which is the genetic information of an animal is isolated from a blood or a cheek swab sample. Then the genes of interest are amplified a million-fold by PCR (polymerase chain reaction) to facilitate the following analysis. The analysis is automatically performed by a genetic analyzer and reveals the gene sequence of the region of interest.
Therefore, the mutations leading to the different coat colours can be seen directly and heterozygous carriers of these mutations can also be identified. Since the test is done mainly automatically, laboratory errors can be widely excluded.
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| Interpretation of the test results | | | | The test results will be submitted separately for each coat colour, so that the genotype for each corresponding gene locus will be given.
Test results exemplary for cinnamon:
Genotype BB: the cat is homozygous for the wild type allele. The cat does not carry cinnamon and will not pass it onto its offspring.
Genotype Bb1: the cat is heterozygous for the cinnamon allele. The cat carries cinnamon and can pass the gene onto its offspring with a probability of 50%.
Genotype b1b1: the cat is homozygous for the cinnamon allele. The cat will phenotypically show cinnamon coat colour (maybe in diluted form as fawn) and will pass the gene onto its offspring with a probability of 100%.
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| Test requirements and duration of the test | | | | The test is performed out of EDTA whole blood (0.5-1 ml) or special cytobrushes. These cytobrushes are available upon request *. Testing is performed a few times per week. The results are due about 5-7 working days after arrival of the sample in our laboratory. For further information please contact Dr. Petra Kühnlein or Dr. Ines Langbein-Detsch
LABOKLIN GmbH u. Co.KG, Prinzregentenstr. 3, D-97688 Bad Kissingen
Phone: +49-971/72020, Fax: +49-971/7236-193, Email: labogen@laboklin.de
* You can order cytobrush test kits by email (see above). Please let us know your complete postal address and how many sets you need.
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