Recognised Mutations of Cat Body Type

Just like people and all other creatures great and small, the normal genetic sequencing and physical appearance of the cat will occasionally throw up an anomaly or mutation that causes a departure from the norm in terms of some aspect of the physical appearance of the cat in question.

In the wild, these genetic anomalies would usually fail to be bred in great numbers into the subsequent offspring of cats carrying the genetic mutation, as the anomalous gene is often recessive. Even in the case of dominant genes, sometimes when the gene is present in a pair (such as if both parent cats carry the gene) this can result in unviable embryos or sterility in subsequent offspring.

However, many naturally occurring genetic anomalies that have led to a certain unusual physical trait in the cat have proven to be appealing and desirable to some cat lovers and breeders. Human intervention into the natural breeding process of cats has perpetuated the presence of many different genetic anomalies and even established a variety of breeds for which the anomaly itself is the signature trait.

Some of the most common recognised physical mutations, plus details of the breeds that contain them, are detailed below.

Ear variances

The normal feline ear is erect and gently pointed, but various different ear mutations are also possible and seen across some breeds of cat.

• The Fd gene is the gene responsible for the folded over ears of the Scottish Fold cat, and may be accompanied by a range of additional problems such as a thicker than normal tail, skeletal abnormalities and swollen feet and limbs.
• The Cu gene gives the American Curl cat its unusual ears, which start life with a normal upright appearance but gradually begin to curl backwards. No associated health problems or defects have been found to accompany this gene.

Paw variances

Polydactyly is one of the most common paw deviances from the norm in cats, and leads the cats to be born with extra toes. Many different genes are thought to contribute to this anomaly, which is not harmful or problematic for the cats in question. “Polydactyl” is the term used to refer to cats of this type, although it is not a breed in and of itself, and the condition can occur in any breed of cat.

• The Pd gene is the gene that causes both polydactyly and the appearance of “thumbs” upon the cat’s feet, although the “thumb” is not a true thumb! This form of polydactyly is generally not problematic, but occasional problems with fused paws or abnormal claws can accompany the mutation.
• The RH gene, the gene for radial hypoplasia, causes enlarged feet, many extra toes and extra joints in the toes, which can be both painful and crippling for the cats in question. Cats carrying the RH gene should not be bred from.

Tail variances

• The M gene gives the Manx cat its tailless or near-tailless appearance, which can be associated with high foetal and kitten mortality rates when two copies of the gene are present (if both parent cats carry the gene) and sometimes, skeletal defects. The length of the tail is an important factor in assessing risk, and Manx cats with a present but dramatically shortened tail are less likely to suffer from problems than cats with no tail at all.
• The Jb gene gives the Japanese Bobtail its abnormally short tail, but no health issues or harmful defects are associated with this anomaly.

Leg variances

• The Mk gene gives the Munchkin cat its shortened legs, which is sometimes referred to as achondroplasia or dwarfism. However, it is not true dwarfism, as the rest of the cat’s appearance, including the size of the head, is not abnormal. Kitten mortality and unviable embryos are associated with the presence of a double copy of the gene.

Size variances

While both pedigree cats and non pedigree cats come in a variety of sizes and some breeds are generally naturally larger or smaller than others, cats as a general rule follow a reasonably stable pattern of shape and size.

• A germ-cell mutation was found to be present in a Persian cat called Treker in the 1990’s, which led to his subsequent offspring being much smaller than normal (almost half the size of the average Persian cat) but otherwise healthy and in proportion. This gene mutation proved to be dominant, and despite Treker himself being of a normal size, three quarters of the kittens that he sired and also their subsequent offspring all attained a diminutive build thanks to the gene.

These mini-Persians are usually referred to as teacup Persians or toy Persians, as are other smaller-than-normal Persian cats that may or may not be related to Treker, including Persian cats that have been deliberately bred for a small size by other means.

The ethics of deliberately breeding for mutation

Many of the mutations and anomalies mentioned above would naturally die out and not perpetrate themselves in long lines of subsequent offspring without human intervention. Even among the gene mutations that have bee found to have a potential adverse affect on the health and wellness of cats that carry the gene, human intervention into breeding programmes has perpetuated their presence and raised the popularity and desirability of cats of that type.

Understandably, there is a strong moral argument to be made against the case for doing this, and the GCCF (Governing Council of the Cat Fancy) refuses to recognise some breeds of cat that are bred for a specific mutation, such as in the case of the Munchkin cat and the Scottish Fold.

The Munchkin cat is rejected as a breed by the GCCF as the shortened limbs of the breed are considered to be anomalous and a significant and unnecessary deviation from the natural conformation of the cat, that may cause problems with mobility and survival in the wild.

The GCCF rejects the Scottish Fold cat as a viable breed, because the gene anomaly that causes the folded ears is also associated with skeletal abnormalities and significant stiffness and difficulty with mobility as the cats of the breed age.