Editing Horse (section)

==Colors and markings==
{{Main|Equine coat color|Equine coat color genetics|Horse markings}}
[[File:Horsescd1l-095.jpg|thumb|upright=1.4|[[Bay (horse)|Bay]] (left) and [[chestnut (horse color)|chestnut]] (right) are two of the most common coat colors, seen in almost all breeds.|alt=Two horses in a field. The one on the left is a dark brown with a black mane and tail. The one on the right is a light red all over.]]

Horses exhibit a diverse array of [[Equine coat color|coat colors]] and distinctive [[horse markings|markings]], described by a specialized vocabulary. Often, a horse is classified first by its coat color, before breed or sex.<ref>{{cite book|author=Vogel, Colin B.V.M. |title=The Complete Horse Care Manual |publisher=Dorling Kindersley Publishing, Inc. |location=New York |year=1995 |isbn=0-7894-0170-3 |oclc=32168476 |page=[https://archive.org/details/completehorsecar0000voge/page/14 14] |url=https://archive.org/details/completehorsecar0000voge/page/14}}</ref> Horses of the same color may be distinguished from one another by white [[horse markings|markings]],<ref>{{cite book |title=A Basic Guide to Horse Care and Management|author1=Mills, Bruce |author2=Barbara Carne |year=1988 |publisher=Howell Book House |location=New York |isbn=0-87605-871-3 |oclc=17507227|pages= 72–73}}</ref> which, along with various spotting patterns, are inherited separately from coat color.<ref>{{cite journal |url=http://www.thehorse.com/ViewArticle.aspx?ID=4354 |title=A Horse of a Different Color |journal=The Horse |url-access=registration |access-date=2010-02-11 |author=Corum, Stephanie J. |date=May 1, 2003 |archive-date=2015-09-18 |archive-url=https://web.archive.org/web/20150918013937/http://www.thehorse.com/articles/13855/a-horse-of-a-different-color |url-status=live }}</ref>

Many [[Equine coat color genetics|genes]] that create horse coat colors and patterns have been identified. Current genetic tests can identify at least 13 different [[allele]]s influencing coat color,<ref name=UCVGL/> and research continues to discover new genes linked to specific traits. The basic coat colors of [[chestnut (horse color)|chestnut]] and [[black horse|black]] are determined by the [[gene]] controlled by the [[Melanocortin 1 receptor]],<ref name=Marklund1996>{{cite journal |last=Marklund |first=L. |author2=M. Johansson Moller |author3=K. Sandberg |author4=L. Andersson |title=A missense mutation in the gene for melanocyte-stimulating hormone receptor (MC1R) is associated with the chestnut coat color in horses |journal=Mammalian Genome |volume=7 |pages=895–899 |year=1996 |doi=10.1007/s003359900264 |pmid=8995760 |issue=12 |s2cid=29095360}}</ref> also known as the "extension gene" or "red factor".<ref name=UCVGL/> Its recessive form is "red" (chestnut) and its dominant form is black.<ref name=UCDIntro/> Additional [[gene]]s control suppression of black color to [[point coloration]] that results in a [[bay (horse)|bay]], spotting patterns such as [[pinto horse|pinto]] or [[leopard complex|leopard]], [[dilution gene]]s such as [[palomino]] or [[dun gene|dun]], as well as [[gray horse|greying]], and all the other factors that create the many possible coat colors found in horses.<ref name=UCVGL>{{cite web|url= http://www.vgl.ucdavis.edu/services/coatcolorhorse.php|title= Horse Coat Color Tests|access-date= 2008-05-01|website= Veterinary Genetics Laboratory|publisher= University of California|archive-date= 2008-02-19|archive-url= https://web.archive.org/web/20080219095454/http://www.vgl.ucdavis.edu/services/coatcolorhorse.php|url-status= live}}</ref>

Horses that have a white coat color are often mislabeled; a horse that looks "white" is usually a middle-aged or older [[gray horse|gray]]. Grays are born a darker shade, get lighter as they age, but usually keep black skin underneath their white hair coat (with the exception of pink skin under white [[horse markings|markings]]). The only horses properly called [[white horse|white]] are born with a predominantly white hair coat and pink skin, a fairly rare occurrence.<ref name=UCDIntro>{{cite web|url= http://www.vgl.ucdavis.edu/services/coatcolor.php|title= Introduction to Coat Color Genetics|access-date= 2008-05-01|website= Veterinary Genetics Laboratory|publisher= University of California|archive-date= 2017-10-10|archive-url= https://web.archive.org/web/20171010200000/http://www.vgl.ucdavis.edu/services/coatcolor.php|url-status= live}}</ref> Different and unrelated [[Genetics|genetic]] factors can produce white coat colors in horses, including several different alleles of [[dominant white]] and the [[sabino horse|sabino-1 gene]].<ref name=haase2009-similar>{{cite journal |author=Haase B |title=Allelic Heterogeneity at the Equine KIT Locus in Dominant White (W) Horses |journal=PLOS Genetics |volume=3 |issue=11 |pages=e195 |year=2007 |pmid=17997609 |pmc=2065884 |doi=10.1371/journal.pgen.0030195 |author2=Brooks SA |author3=Schlumbaum A |display-authors=3 |last4=Azor |first4=Pedro J. |last5=Bailey |first5=Ernest |last6=Alaeddine |first6=Ferial |last7=Mevissen |first7=Meike |last8=Burger |first8=Dominik |last9=Poncet |first9=Pierre-André |doi-access=free }}</ref> However, there are no "[[Albinism|albino]]" horses, defined as having both pink skin and red eyes.<ref name=Duplicatetest>{{cite journal |title= Genetic mapping of dominant white (W), a homozygous lethal condition in the horse (''Equus caballus'') |author1= Mau, C. |author2= Poncet, P. A. |author3= Bucher, B. |author4= Stranzinger, G. |author5= Rieder, S. |journal= Journal of Animal Breeding and Genetics|volume= 121|doi= 10.1111/j.1439-0388.2004.00481.x |year= 2004 |pages= 374–383 |issue= 6}}</ref>