Currently approximately fifteen genes, each with two or more alleles, cause easily observable differences. In additional, there are polygenetic factors that affect coat color. Color and coat genes encompass a wide variety of modes of inheritance. Other color genes are pleiotropic, causing a number of effects besides color. The temperature sensitive allele of the albino gene causing pointed color in many cats including Siamese, effects the optic nerve pathways.
Dominant white is pleiotropic, epistatic, and has variable expression.
White color apparently results from altered development, particularly programmed cell death, and occasionally causes deafness through hair cell degeneration in the inner ear after birth. The rex genes cause similar phenotypes of curly coats through different genes. Tabby patterns were thought to be created by several alleles of one gene. Data collected from the cat fancy indicates that tabby patterns are probably caused by at least three separate genes with multiple alleles. 44555 Incidence of mediastinal lymphosarcoma in young FeLV-negative pedigreed Oriental Shorthair cats has been observed since the early 1980's.