Munchkin Cat Genetics: A Complete Explanation

Munchkin cat genetics ai-gen 3d image of DNA molecue:

Last updated on July 29th, 2023 at 10:16 am

Few breeds have captured the imagination quite like the Munchkin cat. These feline companions have a distinct charm that sets them apart, yet the Munchkin cat genetics, their existence and their recognition as a distinct breed have been the center of ongoing controversy.

The Munchkin cat’s uniquely short legs are a result of a specific genetic mutation, which has been deliberately propagated to create a new “breed” of cat. This has led to some controversy in the cat community, with some arguing that the practice of selectively breeding for genetic mutations is unethical.

In this article, we’ll take a closer look at Munchkin cat genetics and its impact on their short legs. We will also discuss the origin of munchkins and examine potential physical abnormalities associated with them.

If you want to learn more about what makes a Munchkin cat a Munchkin, read on! By understanding more about Munchkin cat genetics, you can make an informed decision for yourself about whether or not to bring one into your home.

Why Munchkin Cats Have Short Legs

At the heart of the Munchkin cat’s distinctive appearance lies a genetic mutation that affects the length of their legs. Munchkins have shorter legs due to a condition known as “achondroplasia,” a form of genetic osteochondrodysplasia.

This condition impacts the development of the long bones of their legs, resulting in a shorter stature than average.

Munchkin Cat Origins

Observations of cats with short legs were first reported as far back as 1944, with a report of several generations of cats seen with this condition. While that line disappeared, occasional reports of short-legged cats continued to emerge from different regions of the world.

Then, in the early 1980s, a single short-legged cat was discovered in Louisiana which gave birth to a shortlegged kitten. This cat and her kitten formed the basis of a breeding program that eventually resulted in the recognition of the Munchkin as an official cat breed.

If you are interested in a more in-depth look at Munchkin cat origins, please visit our article on that specific subject which you can read here.

Munchkin Cat Genetics: A Detailed Look At The Cause Of Their Short Legs

The specific gene mutation that causes the Munchin cat’s characteristic short legs has been determined to be a mutation in the 168–184 Mb region of the UGDH gene located on the FCA B1 cat chromosome (1). The UGDH gene produces an enzyme, UDP-glucose 6-dehydrogenase.

UDP-glucose 6-dehydrogenase participates in several different metabolic pathways that are responsible for growth and development. This specific mutation of region 168-184 impacts the development of the long bones in the leg of the cat.

The developmental abnormalities related to the mutated UGDH gene appear restricted solely to the limbs of the cat, resulting in a condition that is called disproportionate dwarfism, will all parts of the cat being of normal size and proportions with the exception of the legs.

This UGDH gene mutation follows an autosomal dominant inheritance pattern, meaning that it is not linked to the sex of the parents or the kitten and only one copy of the gene is necessary to create the Munchkin’s short legs.

It is also a lethal dominant mutation, meaning having two copies of the gene is incompatible with life. Embryos that have two copies of the gene do not survive, dying at an early stage of development.

Munchkin cat genetics - grey and white munchkin cat laying on a small stack of books

The Munchkin Dwarfism Gene Mutation Is Unique

Munchkin cats are often called “sausage cats” or “weiner cats”, implying a connection to the “weiner dog” (Dachshund). However, the Munchkin cat genetics behind the short legs is totally different than that of other species.

As explained above, the Munchkin cat’s short legs result from a mutation in the UGDH gene. But in short-legged dogs like the Dachshund and Corgi breeds, their short legs result from a completely different gene – FGF4. And rather than a mutation in the FGF4 gene itself, the canine short-leg mutation is caused by what is called a retrogene insertion.

Retregene insertion is a situation where an extra gene has been inserted into a chromosome, seemingly at random. In dogs, this genetic mutation is known to occur on chromosomes 8 and 12. Some dogs may have one or the other of these two mutations, and some may have both – a condition that results in extra-short legs.

The FGF4 gene mutation, like the Munchkin cat’s UGDH gene mutation, is autosomal dominant. Unlike the UGDH mutation, however, it is not autosomal lethal dominant, meaning a dog can live with two copies of the gene.

Do Munchkin Cats Have Deformities Other Than Their Legs?

The frequency of physical abnormalities in Munchkin cats is not very well understood. In general, responsible breeders find that their cats do not have any abnormalities other than their short legs.

There have, however, been sporadic anecdotal reports of Munchin cats with conditions such as pectus excavatum (a hollowed chest that reduces space for the heart and lungs), lordosis (inward curvature of the spine), and extremely short legs.

At this time, there is no hard evidence that any of these conditions are directly related to the UGDH gene mutation. Still, out of an abundance of caution, the generally recommended breeding strategy is to not breed Munchkin-to-Munchkin at all.

If breeders do choose to breed Munchkins together, then every few matings should include an outcrossing to a non-Munchkin cat to maintain genetic diversity and to reduce the risk of unwanted traits related to Munchkin cat genetics.

More detail on the ethics and strategies for breeding Munchkin cats can be found in these articles:

ai-gen image of a fat grey and white munchkin cat. murder floof.

Conclusion

The Munchkin cat breed has its foundation in a naturally occurring genetic mutation, and a remarkable story of discovery, perseverance, and recognition.

While there has been some controversy over the ethics of propagating a genetic mutation to create the Munchkin cat breed, parallels can be drawn with other species and breeds that also owe their existence to selective breeding to propagate specific genetic mutations.

Many of these, such as the Dachshund and the Corgi, were established long before knowledge of genetics existed. Yet, even today, they remain very popular pets.

The Munchkin cat breed has been established for far less time than many of these other breeds, and as such it remains to be seen whether or not the Munchkin cat will become just as beloved.

For now, we can only admire their unique short-legged cuteness and hope that responsible breeding practices will keep them healthy and happy.

Understanding munchkin cat genetics better helps us make informed decisions about whether or not they would be suitable for our home. With thoughtful consideration of both their appearance and potential health implications, you’ll be able to decide if bringing a Munchkin into your life is right for you!

References:

  1. A structural UGDH variant associated with standard Munchkin cats. BMC Genet. 2020 Jun 30;21(1):67. doi: 10.1186/s12863-020-00875-x https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7325026/

Author

  • Dr. Wendy Wilkins, DVM, PhD

    Dr. Wendy Wilkins is an experienced veterinarian and epidemiologist with over 20 years of expertise. She holds a Doctor of Veterinary Medicine (DVM) degree and a Doctorate in Epidemiology from the University of Saskatchewan. Throughout her career, Dr. Wilkins has excelled in clinical practice, academia, research, and regulatory veterinary medicine. She is a respected voice in knowledge dissemination, delivering factual information in a readable and understandable manner through articles, books, and public engagements.

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