Polydactyl Cat
hi today we will talk about this type of cats they call them Poplydactyl Cat
A polydactyl cat is a cat with a congenital physical anomaly called polydactyly
(or polydactylism, also known as hyperdactyly), which causes the cat to
be born with more than the usual number of toes on one or more of its paws. Cats with this genetically inherited trait are most commonly found along the East Coast of North America (in the United States and Canada) and in South West England and Wales
True polydactyly is a congenital abnormality, genetically inherited as an autosomal dominant trait of the ZRS cis element of the Pd gene with incomplete penetrance.[1]
Normal cats have a total of 18 toes, with five toes on each fore
paw, and four toes on each hind paw; polydactyl cats may have as many as
eight digits on their front and/or hind paws. Both Jake, a Canadian
polydactyl cat, and Paws, an American polydactyl cat, were recognised by
Guinness World Records as having the highest number of toes on a cat, 28.[2] Various combinations of anywhere from four to seven toes per paw are common.[3]
Polydactyly is most commonly found on the front paws only, it is rare
for a cat to have polydactyl hind paws only, and polydactyly of all four
paws is even less common.
Feline radial hypoplasia (see squitten)
is a mimic of polydactyly and is considered a severe condition. Radial
hypoplasia may cause the formation of extra jointed toes, but it is not a
result of the gene normally associated with polydactyls. It thus does
not cause the "mitten cat" or "thumb cat" condition where the extra toes
occur separated from the normal ones just like a dewclaw,
usually associated with an additional pad which makes them look like an
underdeveloped foot sticking out near the base of the normal toes.
Rather, radial hypoplasia-related extra toes are immediately adjacent to
the normal ones, giving the cat overly large, flat feet — colloquially
known as "patty
feet" or "hamburger feet". Though this looks less serious than true
polydactyly (as the feet appear "normal" apart from having one or two
extra toes), breeding such cats will eventually result in severely
disabled offspring.[
History and folklore
The condition seems to be most commonly found in cats along the East Coast of North America (in the United States and Canada)[4] and in South West England, Wales and Kingston-upon-Hull.[citation needed] Polydactyl cats have been extremely popular as ship's cats.[4] Although there is some controversy over whether the most common variant of the trait originated as a mutation in New England or was brought there from Britain, there seems to be agreement that it spread widely as a result of cats carried on ships originating in Boston, Massachusetts, and the prevalence
of polydactyly among the cat population of various ports correlates
with the dates when they first established trade with Boston.[4] Contributing to the spread of polydactyl cats by this means, sailors
were long known to value polydactyl cats especially for their
extraordinary climbing and hunting abilities as an aid in controlling
shipboard rodents.[4] Some sailors thought they bring good luck at sea.[4] The rarity of polydactyl cats in Europe may be because they were hunted and killed due to superstitions about witchcraft.[4]
Genetic work studying the DNA basis of the condition indicates that many different mutations can all lead to polydactyly.[1]
Nobel Prize-winning author Ernest Hemingway was a famous aficionado of polydactyl cats, after being first given, by a ship captain, a six-toed cat he named Snow White.[5][6][7] Upon Hemingway's death in 1961, his former home in Key West, Florida
became a museum and a home for his cats, and it currently houses
approximately fifty descendants of his cats (about half of which are
polydactyl).[7] Because of his love for these animals, polydactyl cats are sometimes referred to as "Hemingway cats".[7][8]
Genetics
In
the case of preaxial polydactyly of the Maine Coon cat (Hemingway
mutant) a mutation of the cis-regulatory element ZRS (ZPA regulator
sequence) is associated. ZRS is a noncoding element, 800.000 basepairs
remote to the target gene Shh. An ectopic expression of Shh is seen on the anterior side of the limb. Normally Shh is expressed in an organiser region, called the zone of polarizing activity
(ZPA) on the posterior limb side. From there it diffuses anteriorly,
laterally to the growth direction of the limb. In the mutant mirroring
smaller ectopic expression in a new organiser region is seen on the
posterior side of the limb. This ectopic expression causes cell
proliferation delivering the raw material for one or more new digits.[11][1][12]
Polydactyly is a spontaneous complex phenotypic variation,
developed in one generation. In the concrete preaxial form of the
Hemingway mutant the variation is induced by a single point mutation in a
noncoding cis-regulatory element for Shh. In an extensive phenotypic
variation like this, one or more complete digits at each single limb are
developed including nerves, blood vessels, muscles and ligaments. The
physiology of the digits can be perfect. This complex phenotypic result
cannot be explained by the mutation alone. The mutation can only induce
the variation. In the consequence of the mutation thousands of events,
each different from the wildtype, occur on different organisation
layers, i.e. expression changes of other genes, cell-cell signal
exchange, cell differentiation, cell and tissue growth. The summarized
small random changes on all layers build the raw material and the
process steps for the generation of the plastic variation.[3]
The mentioned form of polydactyly of the Hemingway mutant shows a
biased variation. In a recent empirical study first the number of extra
toes of 375 mutant Maine Coon cats were variable (polyphenism)
and second, the number of extra toes followed a discontinuous
statistical distribution. They were not equally distributed as one might
expect of an identical single point mutation. The example demonstrates
that the variation is not explained completely by the mutation alone.[3]
ليست هناك تعليقات:
إرسال تعليق