Not necessarily, they can have colorpoints and not be related to a simese. Just have 2 moggie parents that are color point carriers.It depends a bit where you are, but I'd say that tabby is commonest, followed by black. Both can have white. Blue is quite common, but a colour-point non-pedigree? Someone has let a Siamese or similar out...
Haha no... It may be a cousin to a Simese or other Oriental, but it does not require a Simese to get out and breed with a DSH any longer... I know this because my friend bred her cats (no Simese blood in them) but they did come from a Ragdoll bloodline and they had Color Point kittens that were considered just DSH's.But where did the colour point come from? It arose in the far East, I reckon that any moggie that is carrying in the UK it has a colourpoint pedigree somewhere in it's background. AFAIK the markings on the first Siamese were entirely novel cats.
The Tyrosinase (TYR) gene, also known as the Color gene, produces an enzyme that is required for melanin production. Mutations in TYR have been associated with temperature-sensitive pigment production that results in colors known as Burmese and Siamese. The wild type phenotype is full color. The Burmese phenotype results from reduced pigment production changing black pigment to sepia and red to cream. The Burmese points are darker than the body and the eyes are yellow-gray or yellow-green. The Siamese phenotype reduces pigment production to the points and the eyes are blue. The wild type (C) allele is dominant to Burmese (cb). Burmese is incompletely dominant to Siamese (cs); Burmese and Siamese heterozygotes (cb/cs) are intermediate in color (mink).These tests identify carriers of Burmese (also called sepia) and Siamese pointed coloration.
A very rare allele of TYR produces an albino phenotype with white coat and blue eyes. The current tests do not detect this rare form.