All domestic cats are descended from a wild ancestor (probably either Felis silvestris or Felis lybica) a mackerel tabby patterned animal, and thus all domestic cats are of an underlying genetic tabby pattern. All cats have 19 pairs of chromosomes upon which there are many thousands of genes that govern the eventual shape, size, sex, colour, pattern and hair length of the individual animal. Over the generations a number of mutations have occurred and selective breeding has been used to isolate these to produce the various pedigree breeds we see today. The mapping of the feline genome has indentified the genes that control coat, colour and pattern in cats along with those that control body size, shape and conformation and those which control diseases and structural abnormalities.
See also the Genetic Testing page on this website