The munchkin is a relatively new breed created by a mutation that causes achondroplasia, or possibly Hypochondroplasia, resulting in breeds with abnormally short legs. At one extreme, some governments consider the munchkin breed to be simply "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. 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 breed.

On the other hand, among the cat fancies that recognise the breed are The International Cat Association (though this has been criticised by some senior members of the Association), the Southern Africa Cat Council, and the Waratah National Cat Alliance in Australia.


Although the genetic abnormality causing the short-legged trait in munchkin cats is often called achondroplasia,

As well as shorter limbs, munchkin cats are more prone to Lordosis and Pectus excavatum than other cats.[1] Small Litter (animal) sizes when two munchkin cats are crossed indicate that Embryos that are Homozygous for the munchkin gene are non-viable.[1]


The munchkin gene is an Autosomal dominant one.[2] 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.[1] 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 squaresRectify

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 kitten will not, as it does not have a copy of the munchkin gene.

Mating two munchkins:
M m
m Mm mm

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

Mating a munchkin with 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 alsoRectify

  • Scottish Fold, a variety of cat with a gene causing Osteochondrodysplasia rather than Achondroplasia

External linksRectify

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