What is a dilute coat?
Dilution is a coat colour caused by the dilute gene which alters the coat colour from black to grey, red to cream and chocolate to lilac and can be found in both purebred and random-bred cats.
Dilution is caused by a single base deletion 1 bp in the melanophilin (MLPH) gene. This gene provides instructions for making melanophilin, a carrier protein that is 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).
Melanin synthesis is normal in the dilute cat, however, the pigment granules are enlarged and deposited unevenly in the hair. The result is clumps of melanin in varying sizes along the hair shaft and areas which lack pigment, producing the illusion of a lighter coat colour.
The dilution gene is recessive, therefore the cat must inherit two copies (one from each parent) for dilution to occur.
What is a dilute carrier?
Dominant genes are always UPPERCASE, and recessive genes are lowercase. In the case of dilution, the dominant gene for full colour is D and the recessive gene is d.
- Homozygous – Two copies of the same gene (D/D or d/d)
- Heterozygous – Different copies of a gene (D/d)
If the cat is heterozygous (D/d), the dominant full-colour gene will override the recessive dilution gene, and the coat will be full colour. However, because the heterozygous cat also has one copy of the recessive dilution gene, he or she is a carrier for dilution. If the cat mates with a cat that also carries the dilution gene (either homozygous d/d or heterozygous D/d), some of the offspring will be dilute (d/d).
Example one: Two full-colour cats each carry the dilution gene. Below is the likely outcome of this mating (assuming they have four kittens).
- Full colour: One kitten is homozygous for full colour (D/D), and cannot pass on the dilution gene to future offspring.
- Full colour, carrying dilution: Two kittens are heterozygous (D/d), they are full-colour, but carry a copy of the dilution gene which they can pass on to offspring.
- Dilute: One kitten is dilute (d/d), and can only pass on the dilution gene to offspring.
Example two: One cat is homozygous full colour, the other cat is heterozygous, and carries a copy of the dilute gene.
- Full colour: All kittens are full colour, two are homozygous (DD), and cannot pass on the dilute gene to their offspring. Two kittens are heterozygous (D/d) and carry a copy of the dilute gene, which can be passed on to kittens.
Example three: Both cats are dilute.
- Dilute: All kittens are heterozygous for dilute (d/d), and only pass the recessive dilute gene to their offspring.
Are dilute cats rare?
Dilution is less common than full colour, but it is not rare. Dilute is an attractive coat colour, and is especially popular in purebred cats. In fact, the Nebelung, Russian Blue, Korat and Chartreux are all blue (grey) cats and with the exception of the Russian (black and white), do not occur in any other colour.
Chocolate and its dilute version, lilac are common among purebred cats, but reasonably uncommon in random-bred cats.
What does a dilute cat look like?
Dilute solid: Grey, cream or lilac
Dilute bi-colour: Grey and white, cream and white, lilac and white
Dilute calico: Grey, cream and white
Dilute tortoiseshell: Grey and cream
Dilute pointed cat:
DNA testing for dilute
The average cat lover has no need to know if his or her cat carries dilute, but this can be important information for cat breeders. Obviously, if the cat is homozygous for dilute, we can see this because the coat colour is dilute but if the cat is heterozygous, he or she carries dilution, but this is not apparent in the coat colour. DNA tests have now made it possible for cat breeders to test their cats for dilution.