Cat Genetics 3.0: Simple Genetic Diseases
The prevalence of genetic diseases in our cats is a recognized and long-standing problem, and the problem is twofold. First and obviously, we have cats that are sick because of a genetic disease. Secondly and more insidiously, we have cats that are perfectly healthy but who are carriers for the disease-causing mutation.
These carrier animals can give us sick animals in future generations. We can identify the sick animals relatively easily, however treatments are often limited. Identifying carrier animals is much more of a challenge. And if we want to eliminate genetic diseases from our cat breeds, we have to be able to identify the carrier animals.
Mutations and Diseases, Old and New
Currently there are over 30 genetic diseases described in cats for which the gene and the disease-causing mutation have been identified (for a list and a description of these diseases, please see Labgenvet’s Cat Genetic Disease Search. For some mutations, the genetic disease is restricted to one breed; these mutations tend to be young (or recent) mutations, occurring after the breed was established, generally within the last 50 to 100 years. An example is Mucopolysaccharidosis VI (MPS VI) seen within the Siamese breed.
Other mutations are more widespread, causing a disease that is found in many breeds. These mutations tend to be older (more ancient) mutations, having occurred before or at the beginning of the formation of modern cat breeds. An example is the mutation that causes Pyruvate Kinase Deficiency (PKLR), seen in numerous breeds as well as within the domestic cat population.
Another example of an older mutation is the one that causes PRA-rdAc (Late-onset Blindness), again seen in numerous breeds.
Some mutations have occurred naturally within the domestic cat population and, because of the phenotypic novelty that they produce, have been used to generate new cat breeds. Examples of this include mutations causing hairless or reduced hair phenotypes as well as the mutations that are the basis for the Munchkin breed or the Scottish Curl breed of cats. See Osteochondrodysplasia (Scottish Fold).
The concepts of basic genetics are presented in Labgenvet’s Cat Genetics 1.0: The Basics.
Several concepts are worth reviewing.