Cat body type genetic mutations
Encyclopedia
Cat
s, like all living organisms, occasionally have mutation
s that affect their body type. Sometimes, these cat body-type mutations are striking enough that human
s select for and perpetuate them. This is not always in the best interests of the cat, as many of these mutations are harmful; some are lethal
in their homozygous form.
This page gives a selection of cat body type mutant allele
s and the associated mutations with a brief description.
(recessive). Cats heterozygous for this gene have abnormal tail
s, but unlike the Manx tailless gene, there are no associated skeletal
disorders and the gene is not associated with lethality.
M = Manx
tailless gene (dominant with high penetrance
). Cats with the homozygous genotype (MM) die before birth, and stillborn
kitten
s show gross abnormalities of the central nervous system
. Cats with the heterozygous genotype
(Mm) show severely shortened tail length, ranging from taillessness to a partial, stumpy tail. Some Manx cats die before 12 months old and exhibit skeletal and organ
defects. Because it was discovered in naturally occurring populations of cats, the Manx gene could confer some kind of selective advantage to the cats, or it may simply be an example of the founder effect
. The trait also occurred and died out in Cornwall (peninsular England), but became fixed in the Isle of Man population where outbreeding was not frequent due to isolation.
Shortened tails, most of which are indistinguishable the Japanese Bobtail or the variably expressed Manx mutation, may occur sporadically in any cat breed or mixed-breed population. However, some may be novel mutations that have not been investigated.
There are multiple types of curly-tailed cats whose tails loop over the back or form tight corkscrews. One such mutation has been developed into the American Ringtail but others have been regarded as curiosities and not perpetuated. The gene(s) responsible have not been fully investigated.
gene (dominant). Cats heterozygous for this gene (Mkmk) have shortened leg
s, but are not disabled. They have a ferret-like gait. The homozygous form (MkMk) may be lethal as litter sizes are smaller than average. Although there was initial concern that Munchkin-type cats would have impaired mobility or spinal problems, this was based on comparison with dog breeds and proved to be unfounded due to the cat's more flexible spine. The mutation has occurred naturally in many locations and has also been perpetuated in feral cats without human intervention (Robinson 1999).
The mutation has proven not to be achondroplasia, but is most likely to be either hypochondroplasia or pseudochondroplasia which affect the long bones of the leg while leaving other bodily proportions, especially the head, unchanged.
). A dominant gene that reduces the number of toes resulting in a "lobster-claw" appearance. This is considered an undesirable mutation.
Polydactyl
(extra-toed) cat
s. There are probably many genes, both dominant and recessive, that cause polydactyly in cats. Most cases of polydactyly in cats are perfectly harmless.
Pd = Thumb-cat polydactyly gene. The Pd gene (dominant with incomplete penetrance) causes the benign, pre-axial form of polydactyly where one or more extra toes occur near the dew claw. Often, the dew claw is converted into a thumb
. There are occasional problems such as fused claw
s or claws facing in the wrong direction, but generally, this form of polydactyly is harmless.
On the other hand, the "hamburger-feet" polydactyly gene is associated with gene for radial
hypoplasia
(RH). The 1995 European Convention for the Protection of Pet Animals considers RH an impairing condition. In a scandal
in the late 1990s, an experimental breeder
in Texas
tried to perpetuate this deformity as the "Twisty Cat" breed. Twisty Cats and the Ethics of Breeding for Deformity Mild RH can cause the post-axial form of polydactyly – enlarged paw
s, extra three-joint
ed toes on the outer, little-toe side of the paws, and no thumb. X-ray
s can determine the structure of the extra toes and whether the cat has the gene for RH. Cats with the gene for RH should never be bred. Cats with severe RH have unusually short front legs. They move like a ferret
and they tend to sit like a squirrel
or kangaroo
and are colloquially known as squitten
s. In some RH cats, the forelegs are twisted with the long bones either severely shortened or absent. All polydactyl cats are banned from German
cat show
s, possibly because of confusion with the impairing form of polydactyly associated with RH.
Polydactyl cats are relatively common in southwest Britain
, Norway
, Sweden
, and the eastern coast of the United States
and Canada
, and some parts of Asia
. Sailor
s thought they were luck
y. Various folktales and dubious assumptions about polydactyl cats include that they are superior rodent hunters, that they have better balance on ship
s in storm
y weather, that their paws are natural snowshoe
s, and that the opposable thumbs (in the thumb-cat form of polydactyly) give them a survival advantage.
Ernest Hemingway
collected polydactyl cats, and the descendants of his pets may still be found at the Ernest Hemingway House
in Key West
.
gene (dominant). Cats with this gene have ear
s that start out normal, but gradually curl backwards. So far, no harmful defects have been associated with this gene. Curled ears have also been observed in free-roaming cats in the Greek islands and in a cat in Australia.
Fd = Scottish Fold
gene (dominant with incomplete penetrance). Cats with this gene have ears that curl forward. There are different degrees of folding, and more genes may be involved in the expression of the Fd gene. This gene is associated with bone
and cartilage
defects such as thickened tail and swollen feet. The homozygous form (FdFd) is probably lethal. However many breeders are careful in their breeding programs, so that such defects are kept to a minimum.
Australian Curl – a curl-eared mutation occurred in a female stray cat in Australia
, but was not inherited by her offspring. When the original cat became ill, necessitating spaying, it was impossible to test-mate her sons back to her to identify a possibly recessive curled-ear mutation.
Sumxu
or Chinese Lop-Eared Cat – extinct Chinese Lop-eared cat breed reported between 1700 and 1938 around Peking, most descriptions are based on a specimen in a German museum. The mode of inheritance of its pendulous ears is not known (the name Sumxu results from mistranslations and actually refers to a variety of marten).
Four ears – a recessive mutation that produced four pinnae or ear flaps (the additional pinnae did not lead to additional ear canals and organs of hearing). In a group of four-eared cats studied in 1957, in addition to duplicated ears the eyes were reduced in size, the jaw was slightly undershot and the cats were relatively inactive and lethargic. Researchers believed that the functioning of the brain was affected. Breeding data indicated it was most often lethal with kittens dying in utero. The majority of recently reported four-eared cats have been healthy with various ear configurations suggesting other genes were involved or developmental abnormalities rather than hereditary factors.
Rounded Ears - a rounded ears mutation occurred in a cat in Italy and is being assessed for breed potential. A similar mutation occurred among free-roaming cats in Texas, but died out. The ears have a rounded, rather than pointed, shape.
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, like all living organisms, occasionally have mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
s that affect their body type. Sometimes, these cat body-type mutations are striking enough that human
Human
Humans are the only living species in the Homo genus...
s select for and perpetuate them. This is not always in the best interests of the cat, as many of these mutations are harmful; some are lethal
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
in their homozygous form.
This page gives a selection of cat body type mutant allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
s and the associated mutations with a brief description.
Tail types
Jb = Japanese bobtail geneGene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
(recessive). Cats heterozygous for this gene have abnormal tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
s, but unlike the Manx tailless gene, there are no associated skeletal
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
disorders and the gene is not associated with lethality.
M = Manx
Manx (cat)
The Manx cat , formerly often spelled Manks, is a breed of domestic cat originating on the Isle of Man, with a naturally occurring mutation that shortens the tail...
tailless gene (dominant with high penetrance
Penetrance
Penetrance in genetics is the proportion of individuals carrying a particular variant of a gene that also express an associated trait . In medical genetics, the penetrance of a disease-causing mutation is the proportion of individuals with the mutation who exhibit clinical symptoms...
). Cats with the homozygous genotype (MM) die before birth, and stillborn
Stillbirth
A stillbirth occurs when a fetus has died in the uterus. The Australian definition specifies that fetal death is termed a stillbirth after 20 weeks gestation or the fetus weighs more than . Once the fetus has died the mother still has contractions and remains undelivered. The term is often used in...
kitten
Kitten
A kitten is a juvenile domesticated cat.The young of big cats are called cubs rather than kittens. Either term may be used for the young of smaller wild felids such as ocelots, caracals, and lynx, but "kitten" is usually more common for these species....
s show gross abnormalities of the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
. Cats with the heterozygous genotype
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...
(Mm) show severely shortened tail length, ranging from taillessness to a partial, stumpy tail. Some Manx cats die before 12 months old and exhibit skeletal and organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
defects. Because it was discovered in naturally occurring populations of cats, the Manx gene could confer some kind of selective advantage to the cats, or it may simply be an example of the founder effect
Founder effect
In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall...
. The trait also occurred and died out in Cornwall (peninsular England), but became fixed in the Isle of Man population where outbreeding was not frequent due to isolation.
Shortened tails, most of which are indistinguishable the Japanese Bobtail or the variably expressed Manx mutation, may occur sporadically in any cat breed or mixed-breed population. However, some may be novel mutations that have not been investigated.
There are multiple types of curly-tailed cats whose tails loop over the back or form tight corkscrews. One such mutation has been developed into the American Ringtail but others have been regarded as curiosities and not perpetuated. The gene(s) responsible have not been fully investigated.
Limbs
Mk = MunchkinMunchkin (cat)
The Munchkin is a cat breed created by a naturally occurring genetic mutation that results in cats with abnormally short legs. However, the shortness of their legs does not seem to interfere with their running and leaping abilities...
gene (dominant). Cats heterozygous for this gene (Mkmk) have shortened leg
Leg
Łęg may refer to the following places in Poland:*A former name for the town of Ełk *Part of the Czyżyny district of Kraków*Łęg, Pleszew County in Greater Poland Voivodeship...
s, but are not disabled. They have a ferret-like gait. The homozygous form (MkMk) may be lethal as litter sizes are smaller than average. Although there was initial concern that Munchkin-type cats would have impaired mobility or spinal problems, this was based on comparison with dog breeds and proved to be unfounded due to the cat's more flexible spine. The mutation has occurred naturally in many locations and has also been perpetuated in feral cats without human intervention (Robinson 1999).
The mutation has proven not to be achondroplasia, but is most likely to be either hypochondroplasia or pseudochondroplasia which affect the long bones of the leg while leaving other bodily proportions, especially the head, unchanged.
Paws
Sh = Split Foot (SyndactylySyndactyly
Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and kangaroo, but is an unusual condition in humans.-Classification:...
). A dominant gene that reduces the number of toes resulting in a "lobster-claw" appearance. This is considered an undesirable mutation.
Polydactyl
Polydactyly
Polydactyly or polydactylism , also known as hyperdactyly, is a congenital physical anomaly in humans, dogs, and cats having supernumerary fingers or toes....
(extra-toed) cat
Polydactyl cat
A polydactyl cat is a cat with a congenital physical anomaly called polydactyly , a type of cat body type genetic mutation that causes the cat to be born with more than the usual number of toes on one or more of its paws...
s. There are probably many genes, both dominant and recessive, that cause polydactyly in cats. Most cases of polydactyly in cats are perfectly harmless.
Pd = Thumb-cat polydactyly gene. The Pd gene (dominant with incomplete penetrance) causes the benign, pre-axial form of polydactyly where one or more extra toes occur near the dew claw. Often, the dew claw is converted into a thumb
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
. There are occasional problems such as fused claw
Claw
A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...
s or claws facing in the wrong direction, but generally, this form of polydactyly is harmless.
On the other hand, the "hamburger-feet" polydactyly gene is associated with gene for radial
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
hypoplasia
Hypoplasia
Hypoplasia is underdevelopment or incomplete development of a tissue or organ. Although the term is not always used precisely, it properly refers to an inadequate or below-normal number of cells. Hypoplasia is similar to aplasia, but less severe. It is technically not the opposite of hyperplasia...
(RH). The 1995 European Convention for the Protection of Pet Animals considers RH an impairing condition. In a scandal
Scandal
A scandal is a widely publicized allegation or set of allegations that damages the reputation of an institution, individual or creed...
in the late 1990s, an experimental breeder
Breeder
A breeder is a person who practices the vocation of mating carefully selected specimens of the same breed to reproduce specific, consistently replicable qualities and characteristics....
in Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
tried to perpetuate this deformity as the "Twisty Cat" breed. Twisty Cats and the Ethics of Breeding for Deformity Mild RH can cause the post-axial form of polydactyly – enlarged paw
Paw
A paw is the soft foot of a mammal, generally a quadruped, that has claws or nails. A hard foot is called a hoof. Paws are used to pad feet for walking and increase friction.- Common characteristics :...
s, extra three-joint
Joint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...
ed toes on the outer, little-toe side of the paws, and no thumb. X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s can determine the structure of the extra toes and whether the cat has the gene for RH. Cats with the gene for RH should never be bred. Cats with severe RH have unusually short front legs. They move like a ferret
Ferret
The ferret is a domesticated mammal of the type Mustela putorius furo. Ferrets are sexually dimorphic predators with males being substantially larger than females. They typically have brown, black, white, or mixed fur...
and they tend to sit like a squirrel
Squirrel
Squirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...
or kangaroo
Kangaroo
A kangaroo is a marsupial from the family Macropodidae . In common use the term is used to describe the largest species from this family, especially those of the genus Macropus, Red Kangaroo, Antilopine Kangaroo, Eastern Grey Kangaroo and Western Grey Kangaroo. Kangaroos are endemic to the country...
and are colloquially known as squitten
Squitten
A squitten is a cat with unusually short forelegs or unusually long hind legs that resembles a squirrel. It is an example of a cat body type genetic mutation...
s. In some RH cats, the forelegs are twisted with the long bones either severely shortened or absent. All polydactyl cats are banned from German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
cat show
Cat show
A cat show is a judged event where the owners of cats compete to win titles in various cat registering organizations by entering their cats to be judged after a breed standard. Both pedigreed and companion cats are admissible, although the rules differ from organization to organization...
s, possibly because of confusion with the impairing form of polydactyly associated with RH.
Polydactyl cats are relatively common in southwest Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, and the eastern coast of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, and some parts of Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
. Sailor
Sailor
A sailor, mariner, or seaman is a person who navigates water-borne vessels or assists in their operation, maintenance, or service. The term can apply to professional mariners, military personnel, and recreational sailors as well as a plethora of other uses...
s thought they were luck
Luck
Luck or fortuity is good fortune which occurs beyond one's control, without regard to one's will, intention, or desired result. There are at least two senses people usually mean when they use the term, the prescriptive sense and the descriptive sense...
y. Various folktales and dubious assumptions about polydactyl cats include that they are superior rodent hunters, that they have better balance on ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...
s in storm
Storm
A storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather...
y weather, that their paws are natural snowshoe
Snowshoe
A snowshoe is footwear for walking over the snow. Snowshoes work by distributing the weight of the person over a larger area so that the person's foot does not sink completely into the snow, a quality called "flotation"....
s, and that the opposable thumbs (in the thumb-cat form of polydactyly) give them a survival advantage.
Ernest Hemingway
Ernest Hemingway
Ernest Miller Hemingway was an American author and journalist. His economic and understated style had a strong influence on 20th-century fiction, while his life of adventure and his public image influenced later generations. Hemingway produced most of his work between the mid-1920s and the...
collected polydactyl cats, and the descendants of his pets may still be found at the Ernest Hemingway House
Ernest Hemingway House
The Ernest Hemingway House, officially known as the Ernest Hemingway Home & Museum, was the residence of author Ernest Hemingway in Key West, Florida, United States. It is located at 907 Whitehead Street, near a prominent lighthouse close to the Southern coast of the island. On November 24, 1968,...
in Key West
Key West
Key West is an island in the Straits of Florida on the North American continent at the southernmost tip of the Florida Keys. Key West is home to the southernmost point in the Continental United States; the island is about from Cuba....
.
Ear types
Cu = American CurlAmerican Curl
The American Curl is a breed of cat characterized by its unusual ears, which curl back from the face toward the center of the back of the skull. An American Curl's ears should be handled carefully because rough handling may damage the cartilage in the ear. The breed originated in Lakewood,...
gene (dominant). Cats with this gene have ear
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
s that start out normal, but gradually curl backwards. So far, no harmful defects have been associated with this gene. Curled ears have also been observed in free-roaming cats in the Greek islands and in a cat in Australia.
Fd = Scottish Fold
Scottish Fold
The Scottish Fold is a breed of cat with a natural dominant-gene mutation that makes its ear cartilage contain a fold, causing the ears to bend forward and down towards the front of their head, which gives the cat what is often described as an "owl-like" appearanceOriginally called lop-eared or...
gene (dominant with incomplete penetrance). Cats with this gene have ears that curl forward. There are different degrees of folding, and more genes may be involved in the expression of the Fd gene. This gene is associated with bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
and cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
defects such as thickened tail and swollen feet. The homozygous form (FdFd) is probably lethal. However many breeders are careful in their breeding programs, so that such defects are kept to a minimum.
Australian Curl – a curl-eared mutation occurred in a female stray cat in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, but was not inherited by her offspring. When the original cat became ill, necessitating spaying, it was impossible to test-mate her sons back to her to identify a possibly recessive curled-ear mutation.
Sumxu
Sumxu
The Sumxu, Chinese Lop-Eared Cat, Drop-eared cat, Droop-eared cat, or Hanging-Ear cat, all names referring to its characteristic feature of pendulous ears, was a long-haired lop-eared breed of cat now considered extinct...
or Chinese Lop-Eared Cat – extinct Chinese Lop-eared cat breed reported between 1700 and 1938 around Peking, most descriptions are based on a specimen in a German museum. The mode of inheritance of its pendulous ears is not known (the name Sumxu results from mistranslations and actually refers to a variety of marten).
Four ears – a recessive mutation that produced four pinnae or ear flaps (the additional pinnae did not lead to additional ear canals and organs of hearing). In a group of four-eared cats studied in 1957, in addition to duplicated ears the eyes were reduced in size, the jaw was slightly undershot and the cats were relatively inactive and lethargic. Researchers believed that the functioning of the brain was affected. Breeding data indicated it was most often lethal with kittens dying in utero. The majority of recently reported four-eared cats have been healthy with various ear configurations suggesting other genes were involved or developmental abnormalities rather than hereditary factors.
Rounded Ears - a rounded ears mutation occurred in a cat in Italy and is being assessed for breed potential. A similar mutation occurred among free-roaming cats in Texas, but died out. The ears have a rounded, rather than pointed, shape.