Point coloration: Difference between revisions - Wikipedia

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'''Points''' are specific areas of an [[animal coat]] that are colored differently from the main body colorations. Typical point coloration is represented by a pale body color and relatively darker extremities, such as face, ears, feet, tail, and [[scrotum]].{{r|Steeh}} It is most recognizable in the coloration of [[Siamese (cat)|Siamese cats]], but colored points can be found in many mammal species and some points are lighter than the main body color.

== Temperature-dependent colorpoint ==

== Small animals ==

{{main|Acromelanism}}

In many species, colorpoint patterns come from a genetic mechanism causing pigment to be produced only in cooler areas of the body, called [[acromelanism]]. This can be seen in [[cat]]s, [[dog]]s (rare),{{r|Brancalion2021|p=22}} [[fancy rat]]s, [[guinea pig]]s, and [[rabbit]]s.

<gallery mode="packed" caption="ColorpointTemperature-dependent in small animalscolorpoint>▼

{{See also|Cat coat genetics|Dog coat genetics}}▼

Dark point coloration patterns are seen in [[cat]]s, [[dog]]s (rare), [[fancy rat]]s, [[guinea pig]]s, and [[rabbit]]s and is called [[acromelanism]] or "colorpoint".

Colored points in dogs are lighter than the body coat, and usually tan. Tan points include small patches above the eyes and on the cheeks, the sides of the muzzle, front of neck and chest, lower legs and insides of legs, and under the tail.{{r|Dreger|Chappell}}▼

▲<gallery mode="packed" caption="Colorpoint in small animals>

File:Ghislaine 6028.jpg|Cat

File:Rat siamese.JPG|Fancy rat

File:Himalayan-Guinea pig.jpg|Guinea pig

File:Króliki kalifornijskie 666.jpg|Rabbit

File:Black & Tan kelpie 2.png|Dog with tan points▼

</gallery>

== Dogs ==

▲[[File:Black & Tan kelpie 2.png|Dog with tan points|thumb|upright]]

▲Colored points in dogs are lighter than the body coat, and usually tan. Tan points include small patches above the eyes and on the cheeks, the sides of the muzzle, front of neck and chest, lower legs and insides of legs, and under the tail.{{r|Dreger|Chappell}}

== Horses ==

{{See also|Equine coat color|Equine coat color genetics}}

[[File:Trotting Belgian draft horse.jpg|thumb|A bay horse, showing black points]]

The name given to a [[horse]]'s coat color depends on the color of both the points and the body. Bay horses have a reddish-brown body with black points, which include the mane, tail, lower legs, and ear rims.{{r|SponenbergBellone2017}}

▲{{See also|CatEquine coat geneticscolor#Points|DogEquine coat color genetics}}

In horses, point coloration is most often produced by the action of the [[Agouti signalling peptide|agouti]] gene. It acts on the [[Melanocortin 1 receptor|extension gene]], when present, to suppress black color to all but the extremities of the horse; the legs, mane, tail and tips of the ears. If the extension gene is not present, the effect of agouti is not visible, as there is no black color present to suppress.

{{multiple image|perrow = 2 |total_width=350

|image1 = Nepal, franches-montagnes.jpg

|image2 = Dole eating grass.jpg

|image3 = Red roan Quarter Horse.jpg

|image4 = Walking Red Dun.jpg

|footer = Some horse colors showing points: [[Bay (horse)|Bay]], [[Buckskin (horse)|buckskin]], [[Roan (horse)|roan]], [[Dun gene|red dun]]

}}

When referring to horse colors, the ''points'' are the mane, tail, lower legs, and ear rims. Certain combinations of point color and body color determine most horse color names.{{r|sponen2009|p=7}} For example, a [[Bay (horse)|bay horse]] has a reddish-brown body color with black points,{{r|sponen2009|p=17}} and a [[Buckskin (horse)|buckskin]] is a yellowish horse with black points.{{r|sponen2009|p=42}} Some horse colorations have nonblack points (cream, red or brown), such as the [[Dun gene|red dun]] which has red to brown points.{{r|sponen2009|p=43}}

Other genes [[horse markings|white markings]] may affect a horse's coat color in addition to agouti, and if present, can further alter or suppress black hair color and may mask any point coloration. In particular, [[gray (horse)|Gray]] horses are born dark and lighten with age; if born bay, they will eventually lose point coloration as the body hair silvers with age, though often the points are the slowest areas of the body to go gray.

In a color with points (black or nonblack) the legs are dark and the color goes all the way down to the hoof, whereas in a horse color without points the color just above the hoof is lighter than its body color.{{r|sponen2009|p=7}} [[Roan (horse)|Roan horses]] have white hairs interspersed throughout their body color, but the points are unaffected and remain black,{{r|sponen2009|p=210}} however a horse with [[horse markings#Leg markings|high white leg markings]] might have their points obscured.{{r|sponen2009|p=8}}

Point coloration may also be visible on horses with other [[dilution gene]]s that act upon a bay base coat. These include:

* The [[cream gene]], an [[incomplete dominant]], that when [[heterozygous]] produces [[Buckskin (horse)|Buckskin]]. When homozygous, even point coloration is mostly suppressed, the color is called [[perlino]], and some individuals may have slightly redder hair at the traditional point coloration locations.

* The [[Champagne gene]], which on a bay base produces Amber Champagne.

A dilution gene that produces what looks like point coloration, but from a completely different genetic mechanism is the [[dominance relationship|dominant]] [[Dun gene]], which dilutes the color of the body coat but not the points, including [[primitive markings]]—a dorsal stripe down the back and, less often, horizontal striping on the upper legs. On a bay base coat the dun gene leaves black points, producing a Bay Dun or "Zebra" Dun. But the gene also leaves the points dark when it appears with other base colors. These include the “blue dun” or [[grullo]], which has a black base coat, and the red dun, which has a chestnut base coat.

Similarly, darker coloration at the points is also preserved in horses with the [[roan (horse)|roan gene]], a patterning gene, producing a body coat of mingled white and dark hairs, but leaving the points the darker base color in all horses, not just those carrying agouti.

Most other genes that produce spotting patterns or [[white markings]] allow point coloration produced by agouti to show except where masked by white depigmentation. There are not always separate names for a pattern over a bay base coat, but one exception is the [[Pinto horse|Bay pinto]], sometimes called [[Tricolour (horse)|”tricoloured”]].

<gallery mode="packed">

File:800 Örn frá Arnarstöðum.jpg|White markings may partially or completely mask point coloration in horses

File:Showmanship at Scottsdale 09.jpg|The dun gene leaves the points darker on all base coat colors, not just when agouti is present

File:Red roan Quarter Horse.jpg|The roan pattern allows point coloration to show on the head as well as traditional point locations

</gallery>

{{-}}

== Donkeys ==

[[File:Donkey - Bearizona Wildlife Park (7177920492).jpg|thumb|upright|A donkey with typical light points]]

In [[donkey]]s, the term "points" refers to the muzzle, rings around the eyes, belly, and upper inner legs, which are usually light in color. The mane, tail, and ear rims are referred to as "trim" and roughly correspond to the "points" of horses. Most donkeys have light points. The coat colors without light points may be called "no light points", "dark points", or "black points". Dark points are caused by a recessive allele of agouti found in Normand and Miniature donkeys. The light areas may vary in extent, with some donkeys having a dark nose but with light areas on the insides of the legs.{{r|SponenbergBellone2017sponen2009|pp=133-5}}

== Sheep ==

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[[File:Ram of the Clun Forest breed.jpg|thumb|upright|A sheep showing point coloration of its face, ears, and legs]]

Some breeds of sheep exhibit point coloration with a white fleece and colored head and legs, usually black.{{r|suffolks}} Sheep breeds with black points include: [[Clun Forest sheep|Clun Forest]], [[Dorset Down]], [[Hampshire Down]], [[Norfolk Horn]], [[Oxford Down]], [[Shropshire sheep|Shropshire]], [[Suffolk sheep|Suffolk]], and [[Valais Blacknose]]. Instead of black, [[American Tunis]] sheep have a red face, and [[Wensleydale sheep]] have a blue-grey face.

== Cattle ==

[[File:British White calf trio.jpg|thumb|upright|British White calves]]

In cattle, extreme [[color-sided]]ness creates a colorpoint pattern with a white body and darker ears, nose, and feet. Breeds displaying this pattern include the [[White Park cattle|White Park]], [[British White]] and some [[Irish Moiled]].{{r|porter2016|p=127}}

== See Also ==

* [[Cat coat genetics]]

* [[Dog coat genetics]]

==References==

{{Commonscat|Colorpoint animals}}

{{Reflist|refs=

<ref name="Brancalion2021">{{cite journal |last1=Brancalion |first1=L |title=Canine coat pigmentation genetics: a review |journal=Animal Genetics |date=2022 |volume=53 |issue=1 |pages=3–34 |doi=10.1111/age.13154 |url=https://onlinelibrary.wiley.com/doi/10.1111/age.13154 |access-date=21 August 2024}}</ref>

<ref name="Chappell">{{Cite web |url=http://www.doggenetics.co.uk/tan.html#tan |title=The Agouti Series : Tan Points |website=Dog Coat Color Genetics |first=Jess |last=Chappell}}</ref>

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<ref name="Dreger">{{cite journal|last1=Dreger|first1=Dayna L.|last2=Schmutz|first2=Sheila M.|year=2011|title=A SINE Insertion Causes the Black-and-Tan and Saddle Tan Phenotypes in Domestic Dogs|journal=Journal of Heredity|volume=102|issue=Suppl 1|pages=S11–S18|doi=10.1093/jhered/esr042|pmid=21846741|doi-access=free}}</ref>

<ref name=SponenbergBellone2017"porter2016">{{citeCite book |first1=Valerie |last1=SponenbergPorter |first1first2=Lawrence |last2=Alderson |first3=Stephen J.G. |last3=Hall |first4=D. Phillip |last2last4=BelloneSponenberg |first2year=Rebecca2016 |yearurl=https://books.google.com/books?id=20172UEJDAAAQBAJ |title=EquineMason's ColorWorld GeneticsEncyclopedia of Livestock Breeds and Breeding |edition=4Sixth |publisher=Wiley[[CAB BlackwellInternational|CABI]] | pages isbn= 5, 6, 23, 253, 2759781780647944}} </ref>

<ref name="sponen2009">{{Cite book |title=Equine Color Genetics |first=D. Phillip |last=Sponenberg |edition=3rd |year=2009 |publisher=Blackwell Pub. |isbn= |ol=22501687M}}</ref>

<ref name="Steeh">{{Cite book |title=Cat breeds |first=Judith A. |last=Steeh |year=1984 |publisher=Gallery Books |isbn=0831712023 |ol=24961512M |page=10 |quote=The colorpoint pattern consists of a basic body color and a contrasting point color. The points appear on the cooler extremities of the cat, and have sometimes been called 'temperature points.' The points, which must be well-defined, of a contrasting color, and of the same color density, are the mask, ears, feet, tail, and sex organs. There should not be any ticking or white hairs in the points. The mask should cover the entire face, including the whisker pads, and be connected to the ears by 'tracings' ; it should not, however, extend over the top of the head.}}</ref>