In a purebred Kitty, all four slots of the Cattribute contain the same trait. This makes purebreds particularly effective at breeding Fancy cats and mutating genes. Players use purebreds to breed Fancies because they produce more predictable genetic results, since they have a higher likelihood of passing on that trait. Some players collect, sell, and sire only purebred cats.
If a dame and sire share a gene in common, there’s a chance that gene will appear twice in their offspring. By repeatedly breeding cats with the same genes, it’s possible, over time, to create your own purebred. The process takes time, but results in a highly valuable Kitty.