Roan is the color of the feathers found in many animals, including horses, cattle and dogs. It is generally defined as a mixture of white and pigmented hair color that is not "gray" or faded as the animal ages. There are various genetic conditions that produce colors that are described as "roan" in various species.
Video Roan (color)
Roan horses
A horse with white hair and mixed colors is usually called the roan sound. However, such mixtures, which may appear superficially similar, are caused by a number of separate genetic factors. Identifiable roan types include true or classical roan, lacquer roan, and rabicano, although other currently unknown factors may be responsible for ambiguous "roaning". The gray horses, which become brighter as they age until their hair is almost completely white, may be confused with roan when they are young. Duns, which are solid colored horses that are influenced by dilution factors in their bodies but with darker dots, are sometimes also confused with roans, but they do not have white and colored hair mixed with roan.
The horse with a classical or true roan pattern may be the basic color mixed with the non-pigmented white hair in the body. Except for white markings under the control of other genes, the head, the mane, the tail, and the lower leg are dark. Roan is a simple dominant trait symbolized by the Rn allele. University of California genetic services, Davis of Veterinary Medicine has developed DNA tests that use genetic markers to indirectly determine the number of Rn or rn alleles owned by a horse. The mutation responsible for roan is not yet definitively identified, but it is assigned to equate chromosome 21 (ECA21) in the KIT sequence. The overall effect is the appearance of silver or light to the affected part of the mantle.
The roan feather color description is as follows:
- Red Roan or roan strawberry describes the true or classical roan in the base layer of chestnut. The mane and tail remain red or have only a few white hairs, while the body ranges from almost brown to pink. Geneticists prefer the term "roan chestnut," but the term is not commonly used.
- Bay Roan is really wandering around in the mantle bay. Special shadows depend on the base color of the bay; but the mane, tail, and lower legs are black, and the reddish body mixes with white hair. The head is usually red. Previously, the roans of the bay were put together with a chestnut roan and both were called "red roans."
- Blue Roan is really wandering around in a black coat. The blade, tail, head, and legs remain black, while the body takes on a gray or bluish appearance. Blue roans are sometimes mistaken for ash or grullos. However, Grays fade with age, while roan is not; and grullos are blue dun and have a marking but do not have mixed white hair.
Other feather colors can also be affected by roaning. Some combinations have the same unique terminology applied to common roan colors, although palomino roans are sometimes called honey roans .
Roan imitate
Roan varnish is not a true roan; is actually one of the complex mantle leopard patterns associated with Appaloosa, Knabstrupper, Noriker horses and related breeds. Rabicano is a white pattern that falls into the category of roaning or scattered white hair, a genetics not yet fully understood. Sometimes called beats , common rabicano even in breeds that have neither true roots nor classics, including Arabs and Thoroughbreds. This pattern usually takes the form of white hair that is scattered around the intersection of the stifle and pelvis, and the strange rings of white hair near the base of the tail. This property is called coon tail or skunk tail . Some forms of sabino, which is a pinto pattern, have been creased along the edges of white dots or other markings. Roan horses may not fit the traditional category as there is still much to learn about roan genetics. The existence of other types of roaning conditions not covered by those mentioned here is possible and possible.
Maps Roan (color)
Roan dogs
The genetics behind roan dogs are still unclear, and the current candidate genes have been ruled out. There is still a lot of ambiguity in the terminology of freckled dogs, called roan , checked , stripes and belton context. Roan or unchecked colors are described in many gundog breeds such as English Cocker Spaniels, American Cocker Spaniels, English Springer Spaniels, Spaniel Fields and Brittanys, German Longhaired Pointer, German Shorthaired Pointer, Spinoni Italiani, Lagotto Romagnolos and English Setters, as well as Border Collies and many other breeds.
In dogs, roan only manifests in non-pigmented areas, its presence and shape are determined by other genes. This is very different from the true roan horses and roan horses, who only roam the pigmented areas of their coats and may have white markings. Conversely, dogs with a rumbling or scratching sound are born with clear, open white markings that begin to fill with spots in the following weeks and continue to darken with age. Most breed standards use the terms "unchecked" and "roan" interchangeably, with the first referring to clearly defined spots on a white background and the last to very tight spots so the mixture appears even. The terminology that correlates the underlying fur color with the roan modifiers is often breed-specific, but most standards call the black dog with roaning blue . In breeds characterized by roaning and ticking like the Large Munsterlander, individuals with clear white marks can be called plated . The term belton is provided for the English Language Manager.
In 1957, Little suggested that roan and ticking be controlled separately, and postulated that roan may be homologous with a "milled" coat on mice. This condition in rats is actually homologous to merle, which may be described by some as "roan." In 2007, the gene responsible for cow roan (KITLG) was disputed as a possible cause of roan in dogs. Neither roan nor ticking, if they are independently attributed, seem recessive.
Roan cattle
Cow breeds known for roans are Belgian Blue and Shorthorn. Among the first, the color of the feathers may be solid black, solid white, or blue roan; the latter may be solid red, solid white, or red. Belgian blues also typically show a spotting pattern, which is genetically separated from the roan. As a result, most of the roan cows showed patches of clear, clear white hair, with roan patches. Some roan cows "faint" look solid, but after careful examination found small patches. Roan cattle can not "breed properly" but breeding a white cow to a strong partner will always produce a bull calf. The characteristic white color of Charolais and White Park is not related to roan.
Roan in Shorthorns and Belgian Blues are controlled by the mast cell growth gene (MGF), also called the steel locus , on the bovine chromosome 5. Part of the KIT ligand, the region is involved in many processes of cell differentiation. The growth factor of mast cells encourages the production of pigment by pigment cells, and without it, skin and hair cells lack pigment. With two functional MGF genes (dominant homozygous), cattle are fully pigmented; without the functional MGF gene (homozigos recessive), they are white. MGF-controlled roots occur when cows have one functional gene and one non-functional MGF gene (heterozygote), which results in a coarse mixture of white areas and colored regions.
The reproductive condition of "White Heifer disease," associated with the MGF gene, is characterized by homozygous MGF-cowboys with incomplete reproductive tract.
Root marmot
Guinea pig roan dye is related to microphthalmia. The allele that controls roaning in guinea pigs is not entirely dominant: animals with one copy of the allele will have varying amounts of white hair scattered through their mantle, especially on the back and sides. This is not to be confused with the various 'Magpie', which is a experimental pig that does not have a red pigment because the "chinchilla" allele is also responsible for white and silver white agouti colors.
About 25% of guinea pigs born from two roan mates are completely white, with a constellation of deformity called lethal white syndrome, although it has nothing to do with overo deadly white syndrome in horses or double merle syndrome in dogs. These symptoms include:
- Partial or complete blindness
- Partial or complete deafness
- Microphthalmia or anophthalmia
- Unpaid eyes
- Teeth missing or defective
- Defective molar teeth
- Long root tooth
- Malabsorption in the small intestine, as in some cases lack of intestinal villi
- Increased susceptibility to disease
It should be noted that, unlike the anophthalmic hamster, a non-sterile, lethal white guinea pig. Women may not be able to provide a young life.
The deadly white snake has a declining lifespan in general, although individuals reportedly live up to 6 or 7 years. Many die soon after birth or at the weaning age. With routine dental and dental care, the lethal can live 2-3 years.
See also
- Horsehair Color
- Combine the mantle color genetics
References
External links
- Photographs of Roan English Cockers
Source of the article : Wikipedia
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