Overo

Overo refers to several genetically unrelated pinto coloration patterns of white-over-dark body markings in horses, and is a term used by the American Paint Horse Association to classify a set of pinto patterns that are not Tobiano. Overo is a Spanish word, originally meaning “like an egg."There are at least three genetically different spotting patterns which fall under the "overo" classification: frame overo, sabino overo, and splash or splashed white overo.

To complicate matters further, some of the spotting gene patterns can be combined to produce a horse with multiple color traits, such as the Tovero. The genetics of pinto spotting patterns are still being researched and are not fully understood. Some patterns may be polygenic, dominant, or incomplete dominants, and spoting can be so minimally expressed on an individual that the animal is mistaken for a "solid" colored horse. The sabino pattern is one of the most complex, as there has been one gene identified, SB-1, that creates one type of sabino patterning, but not all sabino-patterned horses carry it. There is a DNA test for the allele associated with the frame overo pattern, which causes the controversial lethal white syndrome, and there is a DNA test for three mutations, SW-1, SW-2, and SW-3, associated with splashed white.

Although the condition lethal white syndrome is also sometimes called "overo lethal white," that term is somewhat a misnomer. Because there are many different ways a horse can be classified as an "overo," and different genes linked to overo patterning, it is not accurate to say the "overo gene" is what "causes" lethal white syndrome. The frame allele is associated with lethal white, but the other genetics, such as horses with sabino and splash alleles, are not. There is a genetic link between splash white and deafness, but the correlation is not yet fully understood.

Read more about Overo:  Frame Overo, Splash Overo, Sabino "Overo", Tobiano, Tovero and Other Mixed Patterns

Other articles related to "overo, overos":

Lethal White Syndrome
... Lethal white syndrome (LWS), also called overo lethal white syndrome (OLWS), lethal white overo (LWO), and overo lethal white foal syndrome (OLWFS), is an autosomal genetic disorder ... white syndrome often exhibit a spotted coat color pattern commonly known as "frame" or "frame overo." Coat color alone does not always indicate the presence of LWS or carrier status, however ...
Cropout
... registered as American Paint Horses, where the term usually refers to horses with overo coloring and whose parents were solid horses not registered with the APHA ... The overo gene is one of the most frequent genetic sources of cropouts in Paint horses, as there are some forms of overo that are recessive genes, and a significant number of cropout Paints are overos ... At one time, the overo gene was thought to be a dominant gene, though it was acknowledged that more than one gene seemed to influence overo color, and overo offspring from ...
Gumstix - Motherboards - Overo Fire
... The Overo Fire was released in April 2009 ... wireless networking and Bluetooth capabilities to the Overo Water module ...
patterns" class="article_title_2">Overo - Tovero and Other Mixed Patterns
... has pinto spotting patterns that show characteristics of both overo and tobiano and probably carries genes for both ... Horses may also have a combination of sabino and frame overo genetics or any other combination of genes, resulting patterns that are difficult to smoothly classify into any one group ...
Lethal White Syndrome - Inheritance and Expression - Heterozygotes
... Main article Overo See also Pinto horse, American Paint Horse, and Cropout Horses heterozygous for the Ile118Lys mutation on the equine endothelin receptor type B gene—carriers of ... On the other hand, over one quarter of Paints registered in the "overo" category were not frames, and conversely, 10% of horses registered as tobiano also carried frame ... In particular, the tobiano pattern, a dominant gene, is epistatic to overo ...