A Natural Genetic Mutation
Munchkins owe their short legs to a naturally-occurring genetic mutation, and not from human manipulation. The gene responsible for the breed's short legs has been likened to the same one that gives Dachsunds and Welsh Corgis their diminutive stature. However, since the spine of a cat is physically different from that of a dog, Munchkins do not suffer spinal problems sometimes associated with those canine breeds. Because of the small gene pool, outcrossing will need to occur for many years to keep the breed healthy.
Dr Solveig Pflueger, a feline geneticist who works for TICA, conducted a 7 year study on the Munchkin, not only did she find that they were a viable stand-alone breed, she fell in love with them and has been breeding them herself, ever since!
The results of her findings were that 'the only thing that the Munchkin trait appears to affect is the long-bone in the legs'. They can run and jump and get into just as much mischief as any other breed. Her studies determined that the short legs were the result of a dominant genetic mutation affecting the long bones of the legs. This mutation apparently occurred spontaneously within the feline gene pool.
Munchkins do not suffer from Achondroplasia, and the only similarity is the short limbs. A shortlegged Munchkin is called standard Munchkin and the longlegged are called non-standard Munchkin.
A good breeder want to be ensure that disreputable people don't take advantage of the Munchkin's popularity by using unethical breeding practices.