Munchkins are not a man made breed. History recorded them in Europe before they were discovered in the USA and developed into a breed.
Munchkins do not carry the dwarfism gene, it is dominant. If you do not see dwarf legs the cat can not produce dwarf legs. The gene can be passed from either sex.
Munchkins come in long hair and short hair only, not curly hair, not hairless, not with curled or folded ears, no short tails not extra toes. These hybrids have other breed names, not Munchkin
Breeding dwarf to dwarf does not produce frankenstein nor dead kittens. The combo of two parents with dwarf genes is lethal in uetero, the kitten never develop.
If you are looking for a cat that will not get on the counter, the Munchkin is not for you. They have all abilities as their long-legged feline friends, albeit the distance is somewhat limited. The CAN jump from floor to counter, couch or bed,
Over 25 years of clinical studies have proven that the Munchkin has no debilitating disease. The gene is different in cats than humans or canines, it is exclusive to cats. They are not susceptible to disc disease or arthritis. Read the Scientific report about Dwarfism in cats.