Gene I: Inhibitor

Genetic terms in cats
Genome of the cat
Dominance of genes
Cat Breeding techniques
Crossing Table 1
Crossing Table 2
Crossing Table 3
Gene A: Agouti
Gene B: Black
Gene C: Full colour
Gene D: Diluted
Gene Dm: Dilute modifier
Gene Fd: Folded ears
Gene I: Inhibitor
Gene L: Shorthair
Gene Mc: Mackerel
Gene O: Orange
Gene S: Piebald spotting
Gene W: White
Gene XY: Sex
Quality Points for Cats


Gene I: Inhibitor (silver)

Gene I, i


Gene I is responsible that the base of the hairs gets silver-white.
It is dominant over its companion i. Therefore gene I must be present only once to see its expression, that the coat gets a silver white underground.

Note that there is a difference between tipping and ticking.
Tipping is, when only the tip of the hair is coloured. Smoke, Shaded and Shell cats have tipped hairs.
Ticking is when the hair shows several bands of colour. Ticked cats are the Abyssinians and Somalis. Ticked tabby is a special tabby pattern, which we will discussed later.

Non-Silver gene i

Gene i is recessive to gene I. Your cat must have ii that its coat doesn't show a silver white underground.

Possible gene combinations

II homozygous
When such cats are used for breeding all their offspring will be silver.
Ii heterozygous
These cats will produce solid coloured and silver offspring.
ii homozygous for being without white underground
All solid coloured cats have this gene combination.


What is the difference between a Smoke, Shaded and Shell and Cameo ?

silver tipped/ticked hairs In smoke cats the silver white band at the hair base can be only seen when you part the hairs. From outside a smoke cat looks like a solid cat. Only when the cat is moving the silver white underground gets visible. You can also see that it is a smoke cat when you look at the eye brows which are silvery, the cat is to be said to have frown markings, also the frill at longhair cats is silvery. To check whether the cat is really a smoke or a solid, part the hairs on the front and on the legs, there must be seen a clear contrast. Sometimes blue cats or cream cats have a lighter undercoat and can be easily mistaken as smoke cats.
In most hypothesis the Smoke (3) is said to be without agouti. Some theories say that there is a different gene for the smoke cats. Think about the smoke spotted Egyptian Mau, where spotting can be seen on a smoke ground, that would mean that these Maus must carry agouti to show the spots.

Shaded and Shell cats are agouti cats. You can see this when they are born, they look like silver tabbies. Shaded and Shell cats are the result of careful selective breeding programs to diminish the tabby pattern.
Shaded (2) cats look darker in their appearance, one third of the hair tips is coloured, the rest of the hair is white. Mostly known are the black silver shaded cats, but the tipping can be of different colours.
Shell (1) cats almost look white, only with very little tipping, one eighth of the entire hair length is coloured. These cats are known as Chinchillas.
Genetically Silver Tabbies (4), Shaded and Chinchillas are the same.

While Smoke have deep copper eyes the Shaded and Shell usually have green eyes - except all the cats with red which have orange eyes. In some federations also shaded and shell cats with orange eyes are recognized, they are called Pewter.
Silver shaded/shell cats with red are sometimes called Cameos, f.e. red shaded cameo or tortie shell cameo.

In Silvers we can have the following gene combinations:

smoke aa I- - For "I-" you can either have II (homozygous for silver) or Ii (heterozygous for silver)
silver shaded A- I-
plus genes for tabby For "A-" you can either have AA or Aa.
For "I-" you can have II or Ii.
Note that silver tabby, shaded and shell have the same genetic code for their coat colour.
silver shell A- I-
silver tabby A- I- Ta-


For "Ta-" you can have TaTa, or Tata.
You find TaTa f.e. in the Somali or Abyssinian.
A- I- Mc-


For "Mc-" you can have McMc or Mcmc.

Note: You may add Ta- or tata to this code.

A- I- mcmc


Note: You may add Ta- or tata to this code.
There are different theories how the silver white band at the hair base gets broader. We will discuss the Wide band gene Wd later.
We will also discuss the Goldens in a later lesson. You probably know that sometimes there are born Goldens from two Silver Shaded/Shell parents.
You missed the silver tabby spotted pattern ? We will deal with Spotted in our lesson when it comes to the various tabby patterns.

How can this theoretical knowledge be used for the breeding practice ?

You want to breed Chinchillas.

If you really want to go for Chinchillas you should not mix them up with silver shaded. Why not ? Both are silver. But you will have to cope with the following problems:

  • Dark backside of the feet in cats which look like Chinchillas, but a Chinchilla should not have those dark patches on the backside of its feet.
  • On one foot the backside is dark, on the other one the backside is light, in a cat which looks like a silver shaded. But silver shaded must have the backside of all four feet coloured.
  • Cats which are inbetween shaded and shell, too light for shaded and too dark for shell.

If you look in the pedigrees of some cats you find them all, silver shaded as well as silver shell, and even smoke. It would be better to stay either with smoke, breed smoke to smoke or smoke to solid, breed chinchillas only to chinchillas and silver shaded only to silver shaded.
If you really want to breed outstanding chinchillas you should not mix them up with silver tabby.
Chinchillas are the product of a very careful selective breeding program to diminish all the tabby pattern on them, to get rid of the rings on the front legs, to get rid of uneven tipping and to have them as light as possible, so that they almost look white with a sparkling silver shine. If you mix them with silver tabby stripes and ghostmarkings will be back soon.

You want to breed Cameos.

This is quite a difficult task, because Cameos should not show any stripes or ghostmarkings. You should not mix them up with silver tabby, because you will have to face the following problems:

  • You will have Cameos with too much ghostmarkings or with very uneven tipping, darker patches in the tipping on the flanks, ringed tails, stripes on the front legs.
  • You will have Red Silver Tabbies with too little tabby markings, the tabby pattern is blurred, especially in longhair cats you can see this quite often.

You should also not mix Red with Cream, because otherwise you will get those problems:

  • The Cream Cameos look reddish, we call it hot cream, especially on the back you can see, that the colour gets a red tinge.
  • The coat of the Red Cameos shows a very pale red. Even the inhibitor gene seems to influence the colour intensity. Red Cameos should show a nice red tipping, not too pale. Otherwise it will be difficult to see a difference between a pale Red Cameo and a hot Cream Cameo.

You see, breeding Cameos means careful selective breeding and not to mix them, neither with Silver Tabbies nor Red with Cream.

[A] [B] [C] [cb & cs] [D] [Dm] [Fd] [I] [L] [Mc] [O] [S] [W] [XY]

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