Cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s, like all living organisms, occasionally have
mutation
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...
s that affect their body type. Sometimes, these mutations are striking enough that
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
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 even
lethal
Lethality (also called deadliness or perniciousness) is how capable something is of causing death. Most often it is used when referring to diseases, chemical weapons, biological weapons, or their toxic chemical components. The use of this ter ...
in their
homozygous
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
Mo ...
form.
This article gives a selection of cat body type mutant
allele
An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution.
::"The chro ...
s and the associated mutations with a brief description.
Tail types
; Jb:
Japanese Bobtail
The Japanese Bobtail is a breed of domestic cat with an unusual bobtail more closely resembling the tail of a rabbit than that of other cats. The variety is native to Japan, though it is now found throughout the world. The breed has been know ...
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
(
autosomal dominant). Cats
homozygous
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
Mo ...
and
heterozygous
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
Mo ...
for this gene display shortened and kinked tails. Cats homozygous for the gene tend to have shorter, more kinked tails.
This can be distinguished
phenotypically
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...
from the Manx cat mutation by the presence of kinking in the tail, often forming what looks like a knot at the distal end of the tail. 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
Penetrance in genetics is the proportion of individuals carrying a particular variant (or allele) of a gene (the genotype) that also express an associated trait (the phenotype). In medical genetics, the penetrance of a disease-causing mutation is t ...
). Cats with the homozygous genotype (MM) die before birth, and
stillborn
Stillbirth is typically defined as fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can result in the feeling of guilt or grief in the mother. The ter ...
kittens show gross abnormalities of the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
.
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 persisted in the Isle of Man population where outbreeding was not frequent due to isolation.
Shortened tails, most of which are indistinguishable from 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
American(s) may refer to:
* American, something of, from, or related to the United States of America, commonly known as the "United States" or "America"
** Americans, citizens and nationals of the United States of America
** American ancestry, pe ...
, but others have been regarded as curiosities and not perpetuated. The gene(s) responsible have not been fully investigated. However, a research study is under way at UC Davis under the guidance of
Leslie A. Lyons
Leslie A. Lyons is an associate professor at University of Missouri College of Veterinary medicine, Veterinary Medicine.
Career
In 2002, Lyons made international headlines by analyzing the DNA of the world's first cloned cat, a kitten named
C ...
, currently at the University of Missouri.
Limbs
; Mk:
Munchkin
A Munchkin is a native of the fictional Munchkin Country in the Oz books by American author L. Frank Baum. They first appear in the classic children's novel ''The Wonderful Wizard of Oz'' (1900) where they welcome Dorothy Gale to their city in ...
gene (dominant). Cats heterozygous for this gene (Mkmk) have shortened
leg
A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element ca ...
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). This gene is the basis for several intentionally
selected breeds of
dwarf cat
Dwarf or dwarves may refer to:
Common uses
*Dwarf (folklore), a being from Germanic mythology and folklore
* Dwarf, a person or animal with dwarfism
Arts, entertainment, and media Fictional entities
* Dwarf (''Dungeons & Dragons''), a humanoid ...
. The mutation has proven not to be
achondroplasia
Achondroplasia is a genetic disorder with an autosomal dominant pattern of inheritance whose primary feature is dwarfism. In those with the condition, the arms and legs are short, while the torso is typically of normal length. Those affected ha ...
, 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 (
Syndactyly
Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and diprotodontia, but is an unusual condition in humans. The term is from Greek σύν, ''syn'' 'together' and δά ...
). A dominant gene that reduces the number of toes resulting in a "lobster-claw" appearance. This is considered an undesirable mutation.
Polydactyl
Polydactyly or polydactylism (), also known as hyperdactyly, is an anomaly in humans and animals resulting in supernumerary fingers and/or toes. Polydactyly is the opposite of oligodactyly (fewer fingers or toes).
Signs and symptoms
In humans ...
(extra-toed) cats. 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
A dewclaw is a digit – vestigial in some animals – on the foot of many mammals, birds, and reptiles (including some extinct orders, like certain theropods). It commonly grows higher on the leg than the rest of the foot, such that in digit ...
. Often, the dew claw is converted into a
thumb. There are occasional problems, such as fused
claw
A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...
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 the gene for
radial
Radial is a geometric term of location which may refer to:
Mathematics and Direction
* Vector (geometric), a line
* Radius, adjective form of
* Radial distance, a directional coordinate in a polar coordinate system
* Radial set
* A bearing f ...
hypoplasia (RH).
The
European Convention for the Protection of Pet Animals
The European Convention for the Protection of Pet Animals is a treaty of the Council of Europe to promote the welfare of pet animals and ensure minimum standards for their treatment and protection. The treaty was signed in 1987 and became effect ...
discourages deliberate breeding of these cats for two reasons, first that it falls under hypertyping (intentional breeding of extreme characteristics), and secondly that the position of the legs are abnormal. In a
scandal
A scandal can be broadly defined as the strong social reactions of outrage, anger, or surprise, when accusations or rumours circulate or appear for some reason, regarding a person or persons who are perceived to have transgressed in some way. Th ...
in the late 1990s, an experimental
breeder
A breeder is a person who selectively breeds carefully selected mates, normally of the same breed to sexually reproduce offspring with specific, consistently replicable qualities and characteristics. This might be as a farmer, agriculturalist, ...
in
Texas
Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
tried to perpetuate this deformity as the "Twisty Cat" breed.
Mild RH can cause the post-axial form of polydactyly – enlarged
paw
A paw is the soft foot-like part of a mammal, generally a quadruped, that has claws.
Common characteristics
The paw is characterised by thin, pigmented, keratinised, hairless epidermis covering subcutaneous collagenous and adipose tissue, ...
s, extra three-
joint
A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...
ed
toes
Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being '' digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being '' pl ...
on the outer, little-toe side of the paws, and no thumb.
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
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
Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern ...
and are colloquially known as
squittens.
In some RH cats, the forelegs are twisted with the long bones either severely shortened or absent.
All polydactyl cats are banned from
German
German(s) may refer to:
* Germany (of or related to)
** Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ge ...
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 (or moggy) cats are admissible, althoug ...
s, possibly because of confusion with the impairing form of polydactyly associated with RH. Polydactyl cats are relatively common in southwest
Britain
Britain most often refers to:
* The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands
* Great Britain, the largest island in the United King ...
,
Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...
,
Sweden, and the eastern coast of the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
and
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, and some parts of
Asia
Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...
.
Sailor
A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship.
The profession of the s ...
s thought they were
luck
Luck is the phenomenon and belief that defines the experience of improbable events, especially improbably positive or negative ones. The naturalistic interpretation is that positive and negative events may happen at any time, both due to rand ...
y. Various folktales and dubious assumptions about polydactyl cats include that they are superior
rodent hunters, that they have better
balance
Balance or balancing may refer to:
Common meanings
* Balance (ability) in biomechanics
* Balance (accounting)
* Balance or weighing scale
* Balance as in equality or equilibrium
Arts and entertainment Film
* ''Balance'' (1983 film), a Bulgaria ...
on
ship
A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...
s in
storm
A storm is any disturbed state of the natural environment or the atmosphere of an astronomical body. It may be marked by significant disruptions to normal conditions such as strong wind, tornadoes, hail, thunder and lightning (a thunderstorm), ...
y weather, that their paws are natural
snowshoe
Snowshoes are specialized outdoor gear for walking over snow. Their large footprint spreads the user's weight out and allows them to travel largely on top of rather than through snow. Adjustable bindings attach them to appropriate winter footwe ...
s, and that the
opposable thumb
The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...
s (in the thumb-cat form of polydactyly) give them a survival advantage.
Ernest Hemingway
Ernest Miller Hemingway (July 21, 1899 – July 2, 1961) was an American novelist, short-story writer, and journalist. His economical and understated style—which he termed the iceberg theory—had a strong influence on 20th-century f ...
collected polydactyl cats, and the descendants of his pets may still be found at the
Ernest Hemingway House
The Ernest Hemingway House was the residence of American writer Ernest Hemingway in the 1930s. The house is situated on the island of Key West in Florida. It is at 907 Whitehead Street, across from the Key West Lighthouse, close to the southern ...
in
Key West.
Ear types
; Cu:
American 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. The breed originated in Lakewood, California, as the result of a spontaneous mutation.
History
The f ...
gene (dominant). Cats with this gene have
ear
An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...
s that start out normal, but gradually curl backwards. So far, no major harmful defects have been associated with this gene, however, due to the more exposed inner ear regular cleaning is required to prevent infection. Curled ears have also been observed in free-roaming cats in the Greek islands and in a cat in Australia.
; Fd:
Scottish Fold
The Scottish Fold is a breed of domestic cat with a natural dominant gene mutation that affects cartilage throughout the body, causing the ears to "fold", bending forward and down towards the front of the head, which gives the cat what is o ...
gene (dominant with
incomplete penetrance
Penetrance in genetics is the proportion of individuals carrying a particular variant (or allele) of a gene (the genotype) that also express an associated trait (the phenotype). In medical genetics, the penetrance of a disease-causing mutation is t ...
). 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
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
and
cartilage defects such as thickened tail and swollen feet. The homozygous form (FdFd) causes severe
osteochondrodysplasia
Osteochondrodysplasia is a general term for a disorder of the development (dysplasia) of bone ("osteo") and cartilage ("chondro"). Osteochondrodysplasias are rare diseases. About 1 in 5,000 babies are born with some type of skeletal dysplasia. Non ...
. Because of this, many breeders only breed folds to non-folds to avoid homozygous folds. However, heterozygous folds may also develop osteochondrodysplasia of lesser severity.
; 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
}
Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 21 ...
, 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.
Fur
The
Sphynx cat
The Sphynx cat (pronounced , ) also known as the Canadian Sphynx, is a breed of cat known for its lack of fur. Hairlessness in cats is a naturally occurring genetic mutation, and the Sphynx was developed through selective breeding of these anim ...
is a
breed of cat known for its lack of
fur
Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket t ...
. Hairlessness in
cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s is a naturally occurring genetic mutation and the Sphynx was developed through
selective breeding
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant m ...
starting in the 1960s.
-
Size
A germ-cell mutation occurred in a male Persian cat called Treker in 1995, resulting in diminutive, but healthy and normally-proportioned, offspring. Treker and the females with which he was mated were normally sized, but 75% of the kittens sired by Treker inherited diminutive stature, but of normal proportions. The gene was found to be dominant and the diminutive offspring were sold as teacup or toy Persians. Teacup/Toy Persians are a separate breed and not all cats advertised under those names result from Treker's dominant mutation. Most teacup and toy size Persian kittens raised now are descendants from Silver and Golden color division to reduce cat size and are in no way related to Treker.
References
Further reading
* Robinson, Roy. "Genetics for Cat Breeders and Veterinarians" Butterworth Heinemann 1999.
Journal of Heredity
{{Cat nav
Mutation
Evolution of mammals