The cream dilution gene has an effect on both red and black pigment and dilutes the basic coat colour to lighter coat shades. In several breeds this is considered a desirable trait. The Cream dilution gene is responsible for the palomino, buckskin, smoky black, cremello, perlino and smoky cream coat colours. A horse can also carry mutations for other modifying genes which can further affect its coat colour. The Coat Colour Cream dilution test (P713) tests for the genetic status of the MATP gene. The MATP gene has two variants (alleles). The allele Cr is semi-dominant. One copy of the Cr allele dilutes the coat colour with a single dose, resulting in palomino, buckskin or smoky black. Two copies of the Cr allele dilute the coat colour with a double dose into cremello, perlino or smoky cream. The effect on black pigment might be very subtle. Horses with two copies of the Cr allele are also called “double-dilutes” or “blue-eyed cream” and they share a number of characteristics. The eyes are pale blue, paler than the unpigmented blue eyes associated with white color or white markings, and the skin is rosy-pink. The allele N is recessive and does not have an effect on the basic colour.
The Coat Colour Cream dilution test encloses the following results, in this scheme the results of the Coat Colour Cream dilution test are shown in combination with the possible results for the tests that determine the basic Coat Colour (Coat Colour Chestnut and Coat Colour Agouti test):
|
Result Cream dilution |
Result Chestnut + Agouti |
Coat Colour |
Description |
|---|---|---|---|
|
N/N |
e/e + A/A, A/a or a/a
|
Chestnut, Sorrel |
Non-dilute. The basic colour is chestnut or sorrel unless modified by other colour modifying genes. It can only pass on allele N to its offspring. |
|
N/N |
E/E or E/e + A/A or A/a |
Bay, Brown |
Non-dilute. The basic colour is bay or brown unless modified by other colour modifying genes. It can only pass on allele N to its offspring. |
|
N/N |
E/E or E/e + a/a |
Black |
Non-dilute. The basic colour is black unless modified by other colour modifying genes. It can only pass on allele N to its offspring. |
|
N/Cr |
e/e + A/A, A/a or a/a
|
Palomino
|
Heterozygous dilute, one copy of the Cr allele. The basic coat colour chestnut/sorrel is diluted to palomino. These colours can be further modified by other colour modifying genes. It can pass on either allele N or Cr to its offspring. |
|
N/Cr |
E/E or E/e + A/A or A/a |
Buckskin |
Heterozygous dilute, one copy of the Cr allele. The basic coat colour bay/brown is diluted to buckskin. These colours can be further modified by other colour modifying genes. It can pass on either allele N or Cr to its offspring. |
|
N/Cr |
E/E or E/e + a/a |
Smoky Black |
Heterozygous dilute, one copy of the Cr allele. The basic coat colour black is diluted to Smoky Black. These colours can be further modified by other colour modifying genes. It can pass on either allele N or Cr to its offspring. |
|
Cr/Cr |
e/e + A/A, A/a or a/a
|
Cremello
|
Double dilute, two copies of the Cr allele. The basic coat colour chestnut/sorrel is diluted to Cremello. These colours can be further modified by other colour modifying genes. It can only pass on allele Cr to its offspring. |
|
Cr/Cr |
E/E or E/e + A/A or A/a |
Perlino |
Double dilute, two copies of the Cr allele. The basic coat colour bay/brown is diluted to Perlino. These colours can be further modified by other colour modifying genes. It can only pass on allele Cr to its offspring. |
|
Cr/Cr |
E/E or E/e + a/a |
Smoky Cream |
Double dilute, two copies of the Cr allele. The basic coat colour black is diluted to Smoky Cream. These colours can be further modified by other colour modifying genes. It can only pass on allele Cr to its offspring. |
