Editing Siamese cat (section)

==Appearance==
[[File:Siamese gene chart.svg|right|thumb|Siamese gene chart]]

The breed standard of the modern Siamese calls for an elongated, tubular, and muscular body and a triangular head, forming a triangle from the tip of the nose to each tip of the ear. The eyes are almond-shaped and light blue, while the ears are large, wide-based, and positioned more towards the side of the head. The breed has a long neck, a slender tail, and fur that is short, glossy, fine and adheres to the body with no undercoat. Its pointed colour scheme and blue eyes distinguish it from the closely related [[Oriental Shorthair]]. The modern Siamese shares the pointed colour pattern with the [[Thai cat|Thai]], or traditional Siamese, but they differ in head and body type.

The [[Point coloration|pointed pattern]] is a form of partial [[albinism]], resulting from a mutation in [[tyrosinase]], an [[enzyme]] involved in [[melanin]] production. The mutated tyrosinase enzyme is heat-sensitive; it fails to work at normal [[Thermoregulation|body temperatures]] but becomes active in cooler (< 33&nbsp;°C) areas of the skin.<ref>{{cite journal
 | author = D. L. Imes|date=April 2006 | title = Albinism in the domestic cat (''Felis catus'') is associated with a ''tyrosinase'' (''TYR'') mutation | journal = Animal Genetics | volume = 37 | issue = 2 | pages = 175–8 | doi = 10.1111/j.1365-2052.2005.01409.x
 | pmid = 16573534
 | pmc = 1464423
|display-authors=etal}}</ref> The heat-sensitive enzyme results in a dark colouration in the coolest parts of the cat's body, like the extremities and the face, which are cooled by the airflow through their [[Nostril|sinuses]]. Siamese [[kitten]]s are cream or white at birth and develop visible points in the first few months of life in colder parts of their body.<ref>{{cite journal|author1=Ye X.C. |author2=Pegado V. |author3=Patel M.S. |author4=Wasserman W.W. Strabismus |title=genetics across a spectrum of eye misalignment disorders|journal=Clinical Genetics|volume=86|issue=2|pages=103–11| doi=10.1111/cge.12367|pmid=24579652|pmc=4233980|year=2014}}</ref> By the time a kitten is four weeks old, the points should be sufficiently distinguishable to recognise which colour they are.{{citation needed|date=January 2024}}

Siamese cats tend to darken with age, and generally, adult Siamese living in warm climates have lighter coats than those in cool climates. Originally the vast majority of Siamese had seal (extremely dark brown, almost black) points, but occasionally Siamese was born with "blue" (a cool grey) points, genetically a dilution of seal point; chocolate (lighter brown) points, a genetic variation of seal point; or lilac (pale warm grey) points, genetically a diluted chocolate. These colours were considered "inferior" seal points and were not qualified for showing or breeding. These shades were eventually accepted by the breed associations and became more common through breeding programmes specifically aimed at producing these colours. Later, outcrosses with other breeds developed Siamese-mix cats with points in other cat colours and patterns, including red and cream points, [[Lynx point|lynx (tabby) points]], and [[Tortoiseshell cat|tortoise-shell]] ("tortie") points. {{Crossreference|(For more information on cat coat terminology, see [[Cat coat genetics]].)}}{{citation needed|date=January 2024}}

In the United Kingdom, all pointed Siamese-style cats are considered part of the Siamese breed.{{citation needed|date=January 2024}} The [[Cat Fanciers' Association]], considers only the four original fur colours as Siamese:
* seal point, 
* blue point, 
* the chocolate point, and
* lilac point.<ref name="CFA Standard">{{cite web |title=Siamese Breed Standard |url=https://cfa.org/siamese/siamese-breed-standard/ |archive-url=https://web.archive.org/web/20210411043105/https://cfa.org/siamese/siamese-breed-standard/ |url-status=dead |archive-date=11 April 2021 |website=Cat Fanciers' Association |access-date=31 January 2024 }}</ref>

Oriental Shorthair cats with colour points in colours or patterns aside from these four are considered Colourpoint Shorthair in that registry. The World Cat Federation has also adopted this classification, treating the [[Colorpoint Shorthair|Colourpoint Shorthair]] as a distinct breed.<ref name="WCF Breeds" />

Many Siamese cats from Thailand had a kink in their tails, but over the years, this trait has been considered a flaw. Breeders have largely eradicated it, but the kinked tail persists among street cats in Thailand.{{citation needed|date=January 2024}}

<gallery widths="200" heights="200" mode="packed-hover">
File:Siamesekittens.jpg|Seal point and chocolate point Siamese kittens
File:Eson6sema.jpg|Blue point Siamese kitten
File:Siam blue point.jpg|Blue point Siamese kitten
File:Siam Lilac Point.jpg|Lilac point Siamese cat
File:Modern Seal Point Female.jpg|Side view of the head of a modern Seal point adult
</gallery>