The munchkin is a relatively new breed created by a mutation that causes achondroplasia, or more likely hypochondroplasia as the skull size is unaffected, resulting in cats with abnormally short legs. However, the shortness of their legs do not seem to interfere with their running and leaping. The breed originated in 1983 when Sandra Hochenedel found an extremely short-legged black cat living under a trailer in Louisiana. This cat, named Blackberry, was pregnant and half of her kittens were born short-legged. One of Blackberry's kittens, a tomcat named Toulouse, became the father of a breeding program that established the breed in North America.

Recognition

While a few cat registries have recognized the breed, others have not, including the Fédération Internationale Féline, which refuses to recognise what they consider a breed based on a "genetic disease", achondroplasia. The Governing Council of the Cat Fancy likewise refuses to recognise the breed, considering this breed and others like it to be "unacceptable" because they are based on an "abnormal structure or development". The breed is also not recognized by the Cat Fanciers' Association.

Among the cat fancies that recognise the breed are The International Cat Association, the Southern Africa Cat Council, and the Waratah National Cat Alliance in Australia.

Advocates and critics

There is controversy among breeders of pedigree cats as to what genetic mutations are abnormal and potentially disadvantageous to the cat. While several dog breeds such as Dachshunds have short legs, some critics note the higher dependence cats put on their legs for climbing ability and overall agility . Some governments consider the munchkin breed to be "malformed animals" and the deliberate breeding of them "unacceptable" because of the "genetic health problems associated with such breeding".But keepers and breeders of munchkins declare them to be "a sound breed" that is "ideal" for small homes and not particularly susceptible to health problems.

Biology

Although the genetic mutation causing the short-legged trait in munchkin cats is often referred to as achondroplasia, it has not yet been proven that the trait is due to a gene at the same locus as causing achondroplasia in humans. Furthermore, while achondroplasia is typically associated with an enlarged head as well as short legs, a combination of features not seen in munchkin cats, the condition has sometimes been referred to as hypochondroplasia instead.

As well as shorter limbs, munchkin cats are prone to lordosis and pectus excavatum, suggesting that Munchkin cats may have a particular predisposition to these conditions. Small litter sizes when two munchkin cats are crossed indicate that embryos that are homozygous for the munchkin gene are non-viable.

Genetics

The munchkin gene is an autosomal dominant one. Homozygous embryos for the munchkin gene are not viable due to gene lethality. Only kittens that are heterozygous for the munchkin gene develop into viable munchkin kittens. Because only heterozygous munchkin cats are able to pass on the gene, all litters with at least one munchkin parent have the possibility of containing all munchkin kittens, all normal kittens, or a combination of munchkins and normal kittens. A litter with two munchkin parents may be all munchkin kittens, all normal kittens, all non-viable kittens with two copies of the munchkin gene, or any combination of the three.

Punnett squares

Punnett squares, in which the M represents the dominant munchkin gene and the m represents the recessive normal gene, may be used to illustrate the chances of a particular mating resulting in a munchkin cat.

Kittens bearing two copies of the munchkin gene (MM) will not survive. Kittens bearing one munchkin gene and one normal gene (Mm) will be munchkins. Kittens bearing two normal genes (mm) will be normal. Mm munchkin kittens will be able to pass on the munchkin gene to their own offspring. Normal mm kittens will not, as they do not have a copy of the munchkin gene.

Mating two munchkins: M m M MM Mm m Mm mm

For each kitten born from this mating, there is a 25% chance it will be non-viable (stillborn), a 25% chance it will be normal, and a 50% chance it will be a munchkin (i.e., show achondroplastic traits).

Mating a munchkinwith a normal cat: M m m Mm mm m Mm mm

For each kitten born from this mating, there is a 0% chance it will be non-viable (unless it has a different, unrelated condition), a 50% chance it will be normal, and a 50% chance it will be a munchkin.

See also

• Cat body type genetic mutations
• Scottish Fold, a variety of cat with a gene causing osteochondrodysplasia rather than achondroplasia.

References

1. Fédération Internationale Feline, Breeding and Registration Rules: 2.7.3 Genetic Diseases
2. Fédération Internationale Feline, Breeding and Registration Rules: 2.7.3 Genetic Diseases
3. The Governing Council of the Cat Fancy, The GCCF says Health Comes First
4. Cat Fanciers' Association, CFA Breeds
5. The International Cat Association, Cat Breeds Recognized by TICAand The American Association of Cat Enthusiasts (ACCE)
6. The World Cat Congress, Minutes of the Meeting of the World Cat Congress, 1999
7. Southern Africa Cat Council, The Southern Africa Cat Council, Breed Standards (Foreign Breeds)
8. Waratah National Cat Alliance, Munchkin Breed Profile
9. Australian Capital Territory, Code of Practice for the Welfare of Cats in the ACT
10. Messybeast.com Cat Resource, Genetic Abnormalities of Cats

External links

• Is tiny Heed the world's smallest cat? The Guinness Book of Records is waiting until this little Munchkin kitten is fully grown to decide if he is a record breaker.