White patterns are caused by many different genes, and combinations of these may result in more extreme expressions. A few examples are: frame, tobiano, sabino, splashed white and dominant white. White markings are usually included in the list.
Patterns can range from a few white hairs on the coat, to a completely white body, often with pink skin. The edges of the patterns can be round, straight, cornered or include vague ‘ticking’ / ‘roaning’.
White patterns can appear on any coat colour, whether diluted, modified or neither. Grey is no exception to this. Remember, grey is a modifier which turns a coat grey as the horse ages. White patterns are white hairs which are often present from birth (though may increase in number later on). As a horse turns grey, the white patterns may become nearly invisible, but they are still there (as evidenced by the pink skin). The grey only masks the white.
Frame is one of the white patterns and once (and sometimes still) called 'overo' or 'frame overo' when people did not yet discern between most white patterns. Its precise history is unknown, but it likely originated somewhere in the United States not too long ago. Therefore, it is only present in American breeds, and horses descending from these breeds. The pattern has since spread to other regions in the world, including Europe and Australia, when horses with the pattern were sold and/or transported overseas.
The appaloosa white pattern is famous for the many coloured spots placed on a seemingly white background. The spots can be any size, ranging from a few white hairs to spots almost the size of a human fist. They can appear only on the horse's rear quarters, or on the entire horse and everything in between. In addition, appaloosa's can also be without spots, but with a varnish roan pattern of white hairs, ranging from a few to a nearly white horse. This pattern is progressive, meaning many horses obtain more white hairs as they age.
PATN1 is the gene responsible for the appaloosa color, however the LP gene is needed for the expression of the leopard pattern. The LP allele, also known as varnish roan, is needed as a basis to create the famous spotted appaloosa horse.
Splashed White 3
Tobiano is a white pattern based very close to the KIT gene. It is also called piebald or skewbald in the UK and one of the easiest recognizable white patterns.
White Spotting (Dominant White)
White Spotting, also known as Dominant White, is a general name given to a large number of white spotting patterns which are caused by mutations in the KIT gene. As of today, a total of 27 white spotting patterns have been found.