Tobiano
The most common piebald pattern in domestic horses is called tobiano or dominant plate check .
Word origin
The name Tobiano comes from 19th century South America. A General Tobias led a cavalry division, the horses of which were mostly Tobiano-piebald, in the battle of Buenos Aires against the Spaniards.
Appearance
Most of the piebald horses in Europe are Tobianos. The spots on these horses are sharply defined and have smooth edges. The eyes are mostly dark.
Usually a Tobiano has white feet or even more pronounced leg markings. The head markings are not more pronounced than in an otherwise equally predisposed horse without a Tobiano gene. Often there are no badges at all.
In contrast to those of the frame overo, the white spots usually cross the back line in at least one point.
A horse with a low plate or Tobiano check often only has white leg markings. With a little more white, there are also small spots on the middle of the back that point towards the stomach.
A Tobiano or platter with a lot of white usually has the last black spots on the head. If it has a little more black also on the tail (two-colored tail), at the bottom in front of the attachment of the hind leg (loin area) and in front of the chest.
Sometimes, especially in homozygous Tobianos, small black dots (inkspots) can appear between the spots.
In the places where there are no white spots, the horse looks like it would without the piebald gene. So there are blacks, browns, foxes, falcons, Isabels, and Roans with plate checks.
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| Almost monochrome Lewitzer with Tobianogen: Note the white areas on the mane, the croup and the four white legs as Tobian features. | Brown check: Here the Tobiano check is clearly recognizable as a check. | Brown corner: It is typical that head badges are often missing. | Black check with lots of white | Rappschecke: Apart from the head, most of it is white. |
genetics
The Tobiano check is inherited dominantly, i.e. horses that have the gene twice look almost exactly the same as horses that only have it once. It is a weakened form of leucism . The white spots occur because not all skin areas are colonized by melanocytes (cells that produce dye).
The gene for spotting is abbreviated to To for Tobiano. A mutation in which part of intron 13 of the kit locus is reversed was used as a gene test for Tobiano. Since 14% of the Tobianos do not carry this mutation in the Lewitzer, it cannot be the cause of the spotting. Another twisted point is just behind the c-kit locus. It is almost certainly the causative mutation, as it is associated with the piebald in all of the breeds studied so far. The spotting is probably due to the fact that gene areas were cut that are used to determine how often the KIT protein should be produced.
The kit gene itself is on horse chromosome 13 (ECA13) and is at stichelhaarigen horses , the dominant white color of the horse and the Sabinoscheckung mutated. The Tobiano mutation is always inherited together with the healthy KIT gene because of the short distance to this gene. If a horse breeds one of these four genes (that is, has the gene twice), it cannot have either of the other two genes. If it is not inherited, it can have at most two of these predispositions.
When a horse has both the Overo and Tobianogen, it mostly looks like a Tobiano.
The horse's extension locus is on the same chromosome close to the cKit locus , so that the predisposition for chestnut color is often inherited together with the spotted.
Races
The Lewitzer breeding standard stipulates that they have to be Tobiano checks.
The Tobianogen is the most common piebald gene. In breeds where spotting is desired, the majority of the animals have this spotting gene, such as the Arabian pinto , the paint horse and the tinker .
See also
Web links
swell
- ↑ Samantha Ann Brooks: STUDIES OF GENETIC VARIATION AT THE KIT LOCUS AND WHITE SPOTTING PATTERNS IN THE HORSE. Dissertation . University of Kentucky, 2007.
- ↑ a b c d e f g American Paint Horse Association's Guide to Coat Color Genetics; Status 12/2006; http://www.apha.com/
- ↑ a b c d e f g Taktklar: Licht und Schatten - Schecken / Tobiano ( Memento from September 27, 2007 in the Internet Archive )
- ^ SA Brooks, RB Terry, E. Bailey: A PCR-RFLP for KIT associated with tobiano spotting pattern in horses. In: Anim Genet. 33 (4), 2002 Aug, pp. 301-303. PMID 12139510
- ^ A b SA Brooks, TL Lear, DL Adelson, E. Bailey: A chromosome inversion near the KIT gene and the Tobiano spotting pattern in horses. In: Cytogenet Genome Res. 119 (3-4), 2007, pp. 225-230. PMID 18253033
- ^ B. Haase, R. Jude, SA Brooks, T. Leeb: An equine chromosome 3 inversion is associated with the tobiano spotting pattern in German horse breeds. In: Anim Genet. 39 (3), 2008 Jun, pp. 306-309. PMID 18410476
- ^ A b Coat color, lethal dominant roan (Phene ID 434, Group 000210) in Equus caballus. OMIA - Online Mendelian Inheritance in Animals. http://omia.angis.org.au/retrieve.shtml?pid=434
- ↑ EM Santschi, PD Vrotsos, AK Purdy, JR Mickelson: Incidence of the endothelin receptor B mutation that causes lethal white foal syndrome in white-patterned horses. In: Am J Vet Res. 62 (1), 2001 Jan, pp. 97-103. PMID 11197568