The White Spotting Factor

Ragdolls are bred for specific patterns of white. The Ragdoll breeder, while maintaining health, temperament, size, and the other aspects important to the Ragdoll breed....  has the additional challenge of trying to understand and control the variable levels of white that are produced by the white spotting factor. To better understand the white spotting factor, the chart below gives a general idea of how each particular pattern will (should) produce when the cat is bred.

The Ragdoll breeders who are active in the show hall have selected for the particular patterns for many years, narrowing the margin of variability. Current theory about the white spotting factor "S" indicates that each cat has a certain level of white (which we have tentatively identified with numbers). S is a dominant gene, s is the recessive (meaning no white).  A cat only needs one copy of this gene to display the trait. The white spotting gene works by slowing the  migration of pigment cells when the kitten is forming... leaving the kitten without pigment (white is a lack of pigment) on the places farthest away from the neural crest (the spine). S  also has a cumulative affect. Two copies of the white spotting gene will show more white than one copy of the gene. (ie mitted + mitted = bicolor) To make discussions easier to understand, we have given numerical values to the different levels of white that are found most frequently and are most desirable in the Ragdoll genepool. S2 indicates the level of white that will produce a mitted pattern. S4 indicates the level of white that will display as a true bicolor pattern. In contrast, the Birman breed has selected for a S1 level for their white spotting and their mitted pattern is the product of S1S1. All levels of white are probably present in the Ragdoll breed genepool, but the S2 and S4 are the currently desirable levels since they are the ones that will produce the three patterns as is described in the Ragdoll breed standards. Most other breeds do not specify the pattern of white, and accept any level of white or no white.

Not all Ragdolls have the exact levels of white indicated in this chart. If your cat is consistently producing kittens with non-conforming markings, it would be helpful to breed to a colorpoint and try to figure out exactly what the levels of white are. Each level of white is fairly consistent in producing what it is, but the white spotting gene is variable and there are instances of what looks like a bicolor may genetically be a mitted with a unusually high expression in that one cat... or vice-versa... breeding to a colorpoint is the best way to determine the actual levels.

I hope you find this chart helpful.

Again, I must thank Isabelle Bellavance for creating the original excel spreadsheet I used to design this custom color table. The designation of these numerical levels was developed and based on information of numerical levels of white spotting as presented in "Robinsons Genetics for Cat Breeders and Veterinarians", as well as the breeding experience of many Ragdoll breeders.