Hi All, I wrote this article recently and would appreciate the input of some of the experts on here such as Magic and Barry Irwin on what is an intersting topic. I sent the pic attached below to the American Paint Horse society and they replied saying :
The filly definitely carries an overo gene, but impossible to know for sure if it’s the sabino gene or another of the overo genes coming through. We have an old, but good article on the sabino gene on our web site at
www.apha.com/breed/pdf/SabinoDec98.pdf
.
.
The lab we refer people to here in the USA for genetic testing is the University of California at Davis. Their web site is
www.vgl.ucdavis.edu
. They have a lot of great information on their site.
Here below is the article I wrote on the subject:
An Irish-bred three year-old filly in the Mike de Kock yard might be the only Sabino thoroughbred in the country.
Princess Patches, who is by Galileo, has two typical markings that point to her carrying the Sabino (SB1) gene, a mutation that was first identified in 2005.
She has a jagged white patch on her belly as well as a white chin, two typical signs of the gene’s presence.
Other typical signs is that she has four white socks, a blaze and also has a white mark on her lower jaw.
Pinto patterns referring to different patterns of white, including the Sabino gene occurrence, are still not recognised by the thoroughbred’s Jockey Club registry as a separate colour.
However, in America pintos with thoroughbred origins are registered under the American Paint Horse Association.
Besides pinto patterns thoroughbreds can also have appaloosa patterns or other patterns that include Birdcatcher spots or, Bend Or spots.
Birdcatcher spots are named after the 1833 thoroughbred Birdcatcher, who had white hairs throughout his flank and base of his tail.
Bend Or Spots are dark spots named after the great 1877 thoroughbred Bend Or, who had such spots.
Thoroughbred colouring and its origins is a fascinating one and courts much debate.
The thoroughbred has two base colours, black and chestnut and these are effected by many modifiers.
Black horses are actually very rare as the agouti allele, which is part of the black gene, causes the black to be diluted.
The three forms of this allele are A-agouti, in which case the horse will be bay, a-non agouti meaning the horse remains black and At-brown, leading to a brown horse.
Brown horses have black coats with brown hairs on their muzzles, flanks, inner forearms, and inner thighs.
They are often confused with dark bays but are genetically different.
Seattle Slew was an example of a brown horse.
The agouti gene lightens the main body colour, although the mane, tail and legs remain black. The most common shades of bay are dark bay, Touch Gold (light bay), red or blood bay, Cleveland Bay (golden undertones with dappling) and wild type bay, where the black on the legs is restricted to just the joints and the pasterns.
Other rare dilution modifiers in the thoroughbred lead to palominos, cremellos, buckskin bays, perlinos, smoky creams and smoky blacks.
The grey gene causes hairs to lose their pigment at a young age and they rapidly become grey, becoming lighter and lighter as they get older. Some of them even become white.
No thoroughbred is born grey, they are usually born chestnut, bay or black, although those that are destined to become grey usually have a few grey hairs around their eyes, muzzle and/or the back of their ears.
Every grey has at least one grey parent.
Some greys that have a chestnut parent are sometimes called roan, although in reality they are greys as the roan colour does not exist in the thoroughbred. There is one exception as a horse called Catch A Bird, who was born in Australia with a brindle coloured coat that had white stripes, has thrown four progeny that appear to be true, dark-headed roans.
Black is dominant over chestnut, meaning that any chestnut, according to the laws of Mendel, will be pure chestnut.
Two chestnuts can therefore only produce a chestnut, while a bay and a chestnut can produce a bay or a chestnut and a bay and a bay can produce a bay or a chestnut.
A pure bay, like Al Mufti, can only have bay progeny (or the occasional grey).
The chestnut shades range from golden, to red, to liver.
Three of the greatest horses in history, Secretariat, Man O’ War and Pharlap, were all nicknamed “Big Red” due to their red chestnut colour, whilst the great Horse Chestnut was also a red chestnut.
Many horses, of course, have white blazes or stars on their faces, and white socks.
The Darley Arabian, one of the three foundation thoroughbred stallions, was a glowing bay with a wide blaze on his face and three white socks.
The skin under white markings has no pigment.
Their origins and the reason why they commonly appear only on the face and on the extremities of the limbs is the cause of much debate.
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