A LITTLE ABOUT DNA
AND COLOUR.


Almost all of us now, not only have our horses' DNA on record to determine parentage, but also have our horses DNA'd to show their true colour. This even though their DNA might show they are not quite the colour they appear.
Just lately, some new colours have been detected and named by various Universities and others.
There is finally a test for the horses we know as Silver Dapple. I added a little about it at the bottom of the page. One of the newest dilution genes discovered, is now officially named "Pearl". It is a Cream-activated, dilution gene. This basicly means that it also reacts with the cream gene. It appears, adding another instance of dilution, if there is a cream gene present. In this case it manifests as a "double dilution" - pearl AND cream. This colour incidentally, was originally called Apricot, since it does give the horse, an Apricot sort of colour.
Regarding Sabino - there are several kinds of Sabino and at present I believe, we only are able to test for Sabino1.
However, there is obviously a great amount of the sabino gene, to be found in the breed today. For those of you who have had your horses' colour determined, but are not quite sure how to read that which was sent to you, maybe the following will help.

TOBIANO
TT... Only Tobiano allele detected. The horse tested homozygous for Tobiano.
nT... Both Tobiano and non-Tobiano alleles detected. The horse is Tobiano heterozygous.
nn... No Tobiano was detected.

SABINO1
Sb1Sb1...Tested homozygous positive (two copies) for the Sabino1 gene mutation.
nSb1...Both normal and Sabino1 alleles detected. Horse tested heterozygous for Sabino1 and carries one copy of the Sabino1 gene mutation.
nn... Tested negative for the Sabino1 gene mutation.

RED FACTOR
ee... Only the red factor detected. The horse tested homozygous for red pigment. The basic color is chestnut or sorrel, but depending on genes at other color loci, the horse could be red dun, palomino, cremello, gray or white.
Ee...Both black and red factors detected. The horse tested heterozygous for the red factor. It can transmit either E or e to its offspring. The basic color of the horse will be black, bay or brown, but depending on genes at other color loci, the horse may be buckskin, zebra dun, grullo, perlino, gray, or white.
EE...Only the black factor detected. The horse tested homozygous for black pigment. It cannot have red foals regardless of the color of the mate. The basic color of the horse will be black, bay or brown, but depending on genes at other color loci, the horse may be buckskin, zebra dun, grullo, perlino, gray or white.

AGOUTI
aa...Only recessive allele detected. Black pigment distributed uniformly. The basic color of the horse will be black in the absence of other modifying genes.
Aa...Horse tested Heterozygous for Agouti. Black pigment distributed in point pattern. The basic color of the horse will be bay or brown in the absence of other modifying genes.
AA...Only dominant allele detected. Black pigment distributed in point pattern. The basic color of the horse will be bay or brown in the absence of other modifying genes.

CREAM DILUTION
CrCr Double dilute...Horse tested Homozygous for Cream Dilution (Two copies of the Cream allele). Chestnut is diluted to cremello; bay is diluted to perlino and black is diluted to smoky cream. These colors can be further modified by the actions of other genes.
nCr Dilute...Horse tested Heterozygous for Cream Dilution (One copy of the Cream allele). Chestnut is diluted to palomino; bay is diluted to buckskin and black is diluted to smoky black. These colors can be further modified by the actions of other genes.
nn Non-dilute...Horse tested negative for Cream Dilution. Basic colors are chestnut, bay, black or brown in the absence of other modifying genes.

SILVER DILUTION
ZZ...Horse tested Homozygous for Silver Dilution (Two copies of the Silver allele detected). Black-based horses will be chocolate with flaxen mane and tail. Bay-based horses will have pigment on lower legs lightened and flaxen mane and tail. No effect on chestnut color.
nZ...Horse tested Heterozygous for Silver Dilution (One copy of the Silver allele detected). Black-based horses will be chocolate with flaxen mane and tail. Bay-based horses will have pigment on lower legs lightened and flaxen mane and tail. No effect on chestnut color.
nn...Horse tested negative for Silver Dilution.

PEARL DILUTION
PrlPrl... Two copies of the altered sequence detected. On a chestnut base color, a uniform apricot color of body hair, mane and tail will result.
nPrl...One copy of the altered sequence detected. If Cream dilution is also present, a pseudo-double Cream phenotype will result.
nn...No evidence of altered sequence detected.




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