Dr. van Haeringen Laboratorium B.V.

K639 Coat Colour E locus, extension


During the last decades, a large number of scientific publications have described the genetic principles of coat colour and coat variation. Coat colours and coat variations are influenced by many hereditary factors. The DNA-tests are based on physiological effects in the body, in which the production and distribution of pigments result in many coat colour variants. In several cases, the coat colour of an animal may only be decided using DNA-tests.

The Extension gene (MCR1 gene) controls the production of black and red pigment. In cats, shades of red color are determined by the dominant Orange gene (O-locus) located on the X chromosome. The genetic background of the O-Locus is still unknown. The Extension gene is also known as E-locus. The Coat Colour E locus, extension test (K639) tests for the genetic status of the E-locus. The E-locus has two variants (alleles). It is presumed that (almost) all cats are fixed for the dominant allele E, they have two copies of the dominant allele E and based on this gene alone could produce both red and black pigment. The recessive allele e results in kittens that are born with a black/brown tabby pattern (blue/apricot in dilute cats). As the kittens mature, the black/blue pigment is replaced by yellow resulting in the golden coat coloration seen in adult cats. Originally it was named X Colour, now it is called Amber. The recessive allele can be present in the Norwegian Forest cat and traces back to a single female ancestor from Norway born in 1981. Cats with two copies of the allele e only have the Amber Coat Colour when the dominant O allele at the O-locus is not present.

Test specific information

Since 2015, two brands have been developed. CombiGen® is mainly directed at veterinarian applications, whereas CombiBreed® is mainly directed at breeders and/or owners.
Detailed information about Coat Colours and Coat Variation is presented at www.combibreed.com.


Most coat colours and coat types are usually visible directly after birth.

Turn Around Time

The turn-around-time of a test depends to a large extent on the logistics of sample transportation to the laboratory. After receiving the sample at the test location, you can normally expect the result within 10 working days. A longer delivery time applies to tests carried out by a Partner Lab.

Location of disease or trait

Genetic factors influencing coat colours and coat types are usually visible on the outside of an individual. Several factors may be hidden by the external variation.

Breed dependence

This DNA test is available for the following breeds: Norwegian Forest. Additional information is available in the Frequently Asked Questions (FAQ).

Sample type

For this DNA test we accept the following materials: Blood EDTA, Blood Heparin, Tissue, Swab. Please contact Dr. Van Haeringen Laboratorium if you wish to submit other material as listed.


Coat colours are based on many genetic factors. For each factor, a separate test result will be returned.


Various genetic factors influencing coat colour and coat types are inherited in a dominant or recessive mode. Coat colours are influenced by a large number of genetic factors.

Severity of Disease

Factors influencing coat colour and coat types are usually not related to diseases.

Code K639

Coat Colour E locus, extension

€ 47,80 (Incl. 21% VAT)
€ 39,50 (Excl. VAT)