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.

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 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.

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.

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.