Tobiano is a spotted color pattern commonly seen in pinto horses, produced by a dominant gene. The tobiano gene produces white-haired, pink-skinned patches on a base coat color. The coloration is almost always present from birth and does not change throughout the horse's lifetime, unless the horse also carries the gray gene. It is a dominant gene, so any tobiano horse must have at least one parent who carries the tobiano gene.
A bay-and-white, or skewbald, tobiano-patterned horse
Other spotting patterns seen in pinto horses include frame overo, splashed white and sabino. In the United Kingdom, tobianos are frequently referred to as "coloured" or as "pied": piebald if black and white, skewbald if white and any base color other than black. Sometimes "painted" is also used.[1]Bay and white tobiano horses are also referred to as tricoloured.
White crossing the back between the withers and the dock of the tail
White is arranged in a vertical pattern
Facial markings are similar to those of a traditionally solid-colored horse. i.e. star, snip, strip, or blaze. Extreme white facial markings suggest the presence of additional color pattern genes beyond tobiano
White patches which are usually rounded or oval in shape, rather than jagged (see overo)
Dark color extending down the neck, giving the appearance of a shield
The word tobiano is of Portuguese origin, first used in Brazil to describe horses brought to Farroupilha's War by Brigadeiro Rafael Tobias de Aguiar. (HOUAISS, A. VILLAR, M. de S. Dicionário Houaiss da Língua Portuguesa. Rio de Janeiro: Objetiva, 2001. p. 2727).[1]
Geneticsedit
Tobiano is a dominant gene, designated TO.[2] Therefore, one parent must be a tobiano for the pattern to occur, and the coat pattern will occur with a single copy of the tobiano gene present (i.e. the horse is heterozygous for tobiano). Furthermore, when a horse is homozygous for tobiano coloring, all of that horse's offspring will be spotted, with only a few exceptions: if either parent passes the dominant gray gene to the foal, then its spots will be visible while it is young, but will gradually become lighter until finally, as the gray gene acts upon all coat colors, the entire horse's coat fades. In the case of horses that are born tobiano but turn gray, the skin will retain pigmented and unpigmented skin beneath its hair that may produce "ghost" markings. A homozygous tobiano that also carries a dilution gene, such as a pinto with a base color of palomino or buckskin, may not reliably produce spotted offspring if bred to another horse with a dilution gene, as a double-dilution may "wash out" the base color.
The tobiano gene itself is not linked to lethal white syndrome. However, some tobiano horses may be carriers of the gene if they have overo ancestors, and thus have produced affected offspring when bred to another horse that is also a carrier.[3] In some cases, a horse which carries both tobiano and overo genetics may display white markings that combine both patterns, and are referred to as toveros.
DNA testingedit
Tobiano occurs due to a chromosomal inversion on ECA3 where the gene order of a section spanning nearly one-third of the chromosome "flipped" during a genetic recombination event. It is thought to be an ancient gene among domestic horses, about 3500 years old, and is widely distributed across many breeds in the world.[1]
Genetic testing is available to help determine the presence of the tobiano gene. Originally, there was no direct test for tobiano; the early tobiano tests utilized six genetic markers, including a marker on the KIT gene on horse chromosome 3, which were closely linked to tobiano but could not be used to officially prove homozygosity.[4] After some years of research from the University of Kentucky, in 2008 the chromosomal inversion that affects regulatory regions of the KIT gene was discovered.[5] This inversion was finally mapped for genetic testing and is now offered by several laboratories.[1] Testing is most often intended to determine homozygosity, but is also useful in cases where a horse has grayed, or if a horse has an unexplained loss of pigmentation.
^ abcdBailey, Ernest; Brooks, Samantha A. (2013). Horse genetics (2. ed.). Wallingford: CABI. pp. 56–59. ISBN9781780643298.
^"Introduction to Coat Color Genetics" from Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web Site accessed January 12, 2008
^Paul D. Vrotsos RVT and Elizabeth M. Santschi DVM. University of Minnesota Genetics Group. "Stalking the Lethal White Syndrome" 2008-10-26 at the Wayback Machine. Paint Horse Journal. July 1998.
^"Tobiano" 2010-05-15 at the Wayback Machinefrom Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web Site accessed January 13, 2008
^"DNA Testing for Tobiano" 2010-09-17 at the Wayback Machinefrom Animal Genetics Incorporated
Further readingedit
"Horse coat color tests" from Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web Site accessed January 12, 2008
"Introduction to Coat Color Genetics" from Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web Site accessed January 12, 2008
January 01, 1970
tobiano, spotted, color, pattern, commonly, seen, pinto, horses, produced, dominant, gene, tobiano, gene, produces, white, haired, pink, skinned, patches, base, coat, color, coloration, almost, always, present, from, birth, does, change, throughout, horse, lif. Tobiano is a spotted color pattern commonly seen in pinto horses produced by a dominant gene The tobiano gene produces white haired pink skinned patches on a base coat color The coloration is almost always present from birth and does not change throughout the horse s lifetime unless the horse also carries the gray gene It is a dominant gene so any tobiano horse must have at least one parent who carries the tobiano gene A bay and white or skewbald tobiano patterned horseA black and white or piebald tobiano patterned miniature horseTobiano horses Other spotting patterns seen in pinto horses include frame overo splashed white and sabino In the United Kingdom tobianos are frequently referred to as coloured or as pied piebald if black and white skewbald if white and any base color other than black Sometimes painted is also used 1 Bay and white tobiano horses are also referred to as tricoloured Contents 1 Characteristics 2 Genetics 3 DNA testing 4 See also 5 References 6 Further readingCharacteristics edit nbsp Shah Jahan on a piebald tobiano Tobiano traits generally include the following White legs from the hocks and knees down White crossing the back between the withers and the dock of the tail White is arranged in a vertical pattern Facial markings are similar to those of a traditionally solid colored horse i e star snip strip or blaze Extreme white facial markings suggest the presence of additional color pattern genes beyond tobiano White patches which are usually rounded or oval in shape rather than jagged see overo Dark color extending down the neck giving the appearance of a shield The word tobiano is of Portuguese origin first used in Brazil to describe horses brought to Farroupilha s War by Brigadeiro Rafael Tobias de Aguiar HOUAISS A VILLAR M de S Dicionario Houaiss da Lingua Portuguesa Rio de Janeiro Objetiva 2001 p 2727 1 Genetics editTobiano is a dominant gene designated TO 2 Therefore one parent must be a tobiano for the pattern to occur and the coat pattern will occur with a single copy of the tobiano gene present i e the horse is heterozygous for tobiano Furthermore when a horse is homozygous for tobiano coloring all of that horse s offspring will be spotted with only a few exceptions if either parent passes the dominant gray gene to the foal then its spots will be visible while it is young but will gradually become lighter until finally as the gray gene acts upon all coat colors the entire horse s coat fades In the case of horses that are born tobiano but turn gray the skin will retain pigmented and unpigmented skin beneath its hair that may produce ghost markings A homozygous tobiano that also carries a dilution gene such as a pinto with a base color of palomino or buckskin may not reliably produce spotted offspring if bred to another horse with a dilution gene as a double dilution may wash out the base color The tobiano gene itself is not linked to lethal white syndrome However some tobiano horses may be carriers of the gene if they have overo ancestors and thus have produced affected offspring when bred to another horse that is also a carrier 3 In some cases a horse which carries both tobiano and overo genetics may display white markings that combine both patterns and are referred to as toveros DNA testing editTobiano occurs due to a chromosomal inversion on ECA3 where the gene order of a section spanning nearly one third of the chromosome flipped during a genetic recombination event It is thought to be an ancient gene among domestic horses about 3500 years old and is widely distributed across many breeds in the world 1 Genetic testing is available to help determine the presence of the tobiano gene Originally there was no direct test for tobiano the early tobiano tests utilized six genetic markers including a marker on the KIT gene on horse chromosome 3 which were closely linked to tobiano but could not be used to officially prove homozygosity 4 After some years of research from the University of Kentucky in 2008 the chromosomal inversion that affects regulatory regions of the KIT gene was discovered 5 This inversion was finally mapped for genetic testing and is now offered by several laboratories 1 Testing is most often intended to determine homozygosity but is also useful in cases where a horse has grayed or if a horse has an unexplained loss of pigmentation See also editAmerican Paint Horse Equine coat color genetics Equine coat color Overo Pinto horse Sabino horseReferences edit a b c d Bailey Ernest Brooks Samantha A 2013 Horse genetics 2 ed Wallingford CABI pp 56 59 ISBN 9781780643298 Introduction to Coat Color Genetics from Veterinary Genetics Laboratory School of Veterinary Medicine University of California Davis Web Site accessed January 12 2008 Paul D Vrotsos RVT and Elizabeth M Santschi DVM University of Minnesota Genetics Group Stalking the Lethal White Syndrome Archived 2008 10 26 at the Wayback Machine Paint Horse Journal July 1998 Tobiano Archived 2010 05 15 at the Wayback Machine from Veterinary Genetics Laboratory School of Veterinary Medicine University of California Davis Web Site accessed January 13 2008 DNA Testing for Tobiano Archived 2010 09 17 at the Wayback Machine from Animal Genetics IncorporatedFurther reading edit Horse coat color tests from Veterinary Genetics Laboratory School of Veterinary Medicine University of California Davis Web Site accessed January 12 2008 Introduction to Coat Color Genetics from Veterinary Genetics Laboratory School of Veterinary Medicine University of California Davis Web Site accessed January 12 2008 Retrieved from https en wikipedia org w index php title Tobiano amp oldid 1216590417, wikipedia, wiki, book, books, library,
