Overo is a term used by the American Paint Horse Association to describe any patterned horse that is not tobiano. There at three genetically different genes lumped into the overo category: frame overo, sabino, and splash white.
A frame overo horse will have horizontally aligned white patches framed by color, hence the name. Overo horses will usually have a bald face, and white patches will seldom cross the topline and chest.
Like tobiano, overo patterns can range from being so minimal the horse looks solid in color, to being nearly completely white.
A frame overo horse will have horizontally aligned white patches framed by color, hence the name. Overo horses will usually have a bald face, and white patches will seldom cross the topline and chest.
Like tobiano, overo patterns can range from being so minimal the horse looks solid in color, to being nearly completely white.
The overo gene can create lethal white syndrome, also known as overo lethal white syndrome, if the gene is homozygous. A foal born with homozygous overo has an underdeveloped colon, and will show signs of colic within the first 24 hours of birth. Due to the inevitable death caused by LWS, foals born with the disease are euthanized to prevent suffering. However, foals born with heterozygous overo will not be born with LWS. When breeding two overo horses in real life, there will always be a 25% chance that a foal will be born homozygous overo.
Genes that are in bold are active on the coat. Genes that are underlined are genes that the horse may carry, but will have no visible effect on the coat.
Gene Sequence
ee · aa · gg · crcr · dd · chch · F_ · zz · stysty · rbrb · rn+rn+ · sb1+sb1+ · w+w+ · to+to+ · Oo · splspl · lplp · patn1patn1 · patn2patn2
Gene Sequence
ee · aa · gg · crcr · dd · chch · F_ · zz · stysty · rbrb · rn+rn+ · sb1+sb1+ · w+w+ · to+to+ · Oo · splspl · lplp · patn1patn1 · patn2patn2