What is a dilute calico Cat?
Also known as a muted calico, a dilute calico cat is a domestic cat with a tri-colour coat comprised of grey (blue) and cream along with areas of white.
The muted grey and cream is caused by a single base deletion 1 bp in the melanophilin (MLPH) gene. This gene provides instructions for making melanophilin, a carrier protein found in pigment-producing melanocytes. Melanophilin is essential for the even distribution, transport, and translocation of melanin (pigment granules). Menalocytes are specialised cells that contain organelles known as melanosomes. Melanosomes synthesise, store and transport melanin out of the cell via the dendrites to neighbouring keratinocytes (keratin producing cells). Production of melanin is normal in the dilute cat, however, the pigment granules are enlarged and deposited unevenly in the hair. The result is clumps of melanin of varying sizes along the hair shaft and areas which lack pigment, producing the illusion of a lighter coat colour. Black becomes grey and orange (red) becomes cream or brown becomes lilac and orange becomes cream.
The dilution gene is recessive, therefore the cat must inherit two copies (one from each parent) for dilution to occur.
In addition to the blue and cream, the dilute calico also has areas of white, predominantly on the underside, caused by the dominant white spotting gene (WS). The WS gene is pleiotropic (a gene that has different effects), and exhibits complete penetrance for the absence of coat pigmentation by disrupting replication and migration of melanocytes into the hair, and incomplete penetrance for hereditary deafness and iris colour. Kittens who inherit two copies of the white spotting gene will have more areas of white than kittens who only inherit one copy.
What breed of cat is a dilute calico?
The dilute calico is a coat pattern and colour and not a breed. Dilute calicos can be found across many breeds of cats as well as random-bred domestics (moggies).
Are dilute calico cats rare?
The dilute calico coat colour and pattern is considerably less common than other coat colours and patterns but is not rare. It certainly is more difficult to find a random-bred or purebred dilute calico than other coat colours and patterns. Dilute calico is accepted in the following breeds:
- American Shorthair
- American Wirehair
- British Shorthair
- Cornish Rex
- Devon Rex
- European Shorthair
- Exotic Shorthair
- Maine Coon
- Selkirk Rex
As the dilution gene is recessive, the cat must inherit a copy from each parent in order for the trait to develop. Cats can have a dense coat colour (black or red), and carry one copy of the dilute gene, and if the other parent also carries a copy of the gene (regardless of whether he or she has a dense coat colour), then there is a 1 in 4 chance the offspring will be calico. Two dilute cats can only ever produce dilute offspring.
Related: Rare cat colours
Dilute male calico cats
Calico occurs almost exclusively in female cats, only 1 – 3,000 male cats are tortoiseshell or calico. The orange and cream gene is carried on the X chromosome. As the male (XY) only has one X chromosome he will either be orange or cream (if dilute) or non-orange. The female (XX) has two X chromosomes, if she inherits one copy of the orange gene and one copy of non-orange (usually black) she will display both colours. That is because each cell contains two X chromosomes. One of which is turned off, in a process known as X inactivation, the result is random patterns of orange and black or cream and blue, if she is dilute.
The most common causes of chimerism are Klinefelter syndrome and tetragametic chimerism.
Klinefelter syndrome is a genetic condition in which the male is born with an extra copy of the X chromosome, making him XXY.
Tetragametic chimerism occurs when early embryos fuse together to create a single organism. In most cases, one cell line will dominate the other, with only small populations of the second DNA within the body.
What is the difference between a dilute calico and dilute tortoiseshell?
The dilute calico coat consists of grey and cream with areas of white with the coloured areas usually occurring in patches.
Dilute tortoiseshell coats are made up of patches of grey and cream with no white, and the distribution of the colour is more of a mosaic pattern.