Roan is a white patterning coat colour trait of intermixed white and coloured hairs in the body while the head, lower legs, mane and tail remain colored. Roan horses are born with the pattern, though it may not be obvious until the foal coat is shed. The white and coloured hairs are evenly mixed in horses that inherit the classic Roan gene, which can differentiate this from several mimic patterns called roaning. Roaning patterns tend to be uneven in the distribution of white hairs and the inheritance of roaning has not been defined. The mutation causing the Roan coat colour has not yet been identified. The Coat Roan test (P659) tests for DNA markers that are associated with Roan coat colour in several breeds, the DNA markers can be used to determine if a horse has the Roan mutation and how many copies. This test detects three variants (alleles), Rn, Rn* and N. The allele Rn is dominant. One or two copies of the Rn allele result in a Roan coat colour. The allele Rn* is very uncommon and not always associated with the Roan coat colour, this allele has only been observed in Tennessee Walking horses and Rocky Mountain horses. The allele N is recessive and does not have an effect on the basic colour.
The Coat Colour Roan test encloses the following results, in this scheme the results of the Coat Colour Roan 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 Roan |
Result Chestnut + Agouti |
Coat Colour |
Description |
|---|---|---|---|
|
N/N |
e/e + A/A, A/a or a/a
|
Chestnut, Sorrel
|
Not Roan. The basic colour chestnut/sorrel is not modified 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 |
Not Roan. The basic colour bay/brown is not modified 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 |
Not Roan. The basic colour black is not modified unless modified by other colour modifying genes. It can only pass on allele N to its offspring. |
|
Rn/N |
e/e + A/A, A/a or a/a
|
Chestnut/sorrel Roan |
One copy of the dominant Rn allele. The colour is chestnut/sorrel roan, unless modified by other colour modifying genes. It can pass on either allele N or Rn to its offspring. |
|
Rn/N |
E/E or E/e + A/A or A/a |
Brown/bay Roan |
One copy of the dominant Rn allele. The colour is brown/bay roan, unless modified by other colour modifying genes. It can pass on either allele N or Rn to its offspring. |
|
Rn/N |
E/E or E/e + a/a |
Black Roan |
One copy of the dominant Rn allele. The colour is black roan, unless modified by other colour modifying genes. It can pass on either allele N or Rn to its offspring. |
|
Rn*/N |
e/e + A/A, A/a or a/a |
Chestnut/sorrel or Chestnut/sorrel Roan |
One copy of the uncommon Rn* allele. The colour can be chestnut/sorrel or chestnut/sorrel roan, unless modified by other colour modifying genes. It can pass on either allele N or Rn* to its offspring. |
|
Rn*/N |
E/E or E/e + A/A or A/a |
Brown/bay or Brown/bay Roan |
One copy of the uncommon Rn* allele. The colour can be brown/bay or brown/bay roan, unless modified by other colour modifying genes. It can pass on either allele N or Rn* to its offspring. |
|
Rn*/N |
E/E or E/e + a/a |
Black or Black Roan |
One copy of the uncommon Rn* allele. The colour can be black or black roan, unless modified by other colour modifying genes. It can pass on either allele N or Rn* to its offspring. |
|
Rn/Rn |
e/e + A/A, A/a or a/a |
Chestnut/sorrel Roan |
Two copies of the dominant Rn allele. The colour is chestnut/sorrel roan, unless modified by other colour modifying genes. It can only pass on allele Rn to its offspring. |
|
Rn/Rn |
E/E or E/e + A/A or A/a |
Brown/bay Roan |
Two copies of the dominant Rn allele. The colour is brown/bay roan, unless modified by other colour modifying genes. It can only pass on allele Rn to its offspring. |
|
Rn/Rn |
E/E or E/e + a/a |
Black Roan |
Two copies of the dominant Rn allele. The colour is black roan, unless modified by other colour modifying genes. It can only pass on allele Rn to its offspring. |
|
Rn/Rn* |
e/e + A/A, A/a or a/a |
Chestnut/sorrel Roan |
One copy of the dominant Rn allele and one copy of the uncommon Rn* allele. The colour is chestnut/sorrel roan, unless modified by other colour modifying genes. It can pass on either allele Rn or Rn* to its offspring. |
|
Rn/Rn* |
E/E or E/e + A/A or A/a |
Brown/bay Roan |
One copy of the dominant Rn allele and one copy of the uncommon Rn* allele. The colour is brown/bay roan, unless modified by other colour modifying genes. It can pass on either allele Rn or Rn* to its offspring. |
|
Rn/Rn* |
E/E or E/e + a/a |
Black Roan |
One copy of the dominant Rn allele and one copy of the uncommon Rn* allele. The colour is black roan, unless modified by other colour modifying genes. It can pass on either allele Rn or Rn* to its offspring. |
|
Rn*/Rn* |
e/e + A/A, A/a or a/a |
Chestnut/sorrel or Chestnut/sorrel Roan |
Two copies of the uncommon Rn* allele. The colour can be chestnut/sorrel or chestnut/sorrel roan, unless modified by other colour modifying genes. It can only pass on allele Rn* to its offspring. |
|
Rn*/Rn* |
E/E or E/e + A/A or A/a |
Brown/bay or Brown/bay Roan |
Two copies of the uncommon Rn* allele. The colour can be brown/bay or brown/bay roan, unless modified by other colour modifying genes. It can only pass on allele Rn* to its offspring. |
|
Rn*/Rn* |
E/E or E/e + a/a |
Black or Black Roan |
Two copies of the uncommon Rn* allele. The colour can be black or black roan, unless modified by other colour modifying genes. It can only pass on allele Rn* to its offspring. |
