One of the remarkable features of the cat is the wide variation of eye color that is inherited independently of coat color. The term eye color refers to the color of the iris.

The normal variation in iris color is quite wide, ranging from rich orange, through shades of yellow and hazel-green to green. The brown and dilute genes (b and d ) do influence pigmentation of the eye, but it seems that the normal variability is due to polygenes and chance which tend to over-ride the effect of the major genes for eye color.

The influence of polygenes means that, within reason, selective breeding can stabilize any desirable eye color. In practice, it is easier to 'fix' extreme shades (such as copper or green) than intermediate ones. An exception to this is the blue eye color of the Siamese and various white breeds which is definitely associated with major genes.

Cats' main eye colors: orange or copper, yellow, hazel, green, blue (as with dominant white), and blue (as in Siamese).

The Main Genes of White Persians

Let's start with the simple stuff: White Persians. First of all, there is no such thing as a White cat; I told you it was simple. What you see when you look at a White cat, is a cat of color wearing a white sweater. What lies beneath that fluffy white exterior is a color shrouded in mystery. With careful study of a pedigree, the underlying color can be fairly accurately revealed but you do need to have a basic understanding of color genetics (see chart below). Even then you may not be absolutely positive but a test breeding can be done to further clarify the suspicions.

Many White kittens are born with a "clarity" spot on top of their heads and careful examination of this spot can reveal the color beneath that lovely white sweater. These "clarity" spots disappear after a few months and the cat will be completely white with no telltale sign of the color secret it holds within.

There are dominant or homozygous Whites (WW) and non-dominate or heterozygous Whites (Ww). White is not carried recessively; at least one parent must be White to produce White kittens. Therefore, non-White kittens resulting from a White parent will not ever produce White kittens. BTW - You cannot breed a White cat to a color cat and get bi-color kittens unless the white cat is masking bi-color. Bi-dolor cats have the "piepald" or spotting gene (Ss and SS). But I digress; back to our white cats:

• If a homozygous white cat mates, all offspring will be white. If two homozygous white cats mate, all offspring will be homozygous white. If a homozygous white cat mates with a heterozygous white cat, there will be both homozygous white and heterozygous white offspring in a 1:1 ratio. If a homozygous white cat mates with a homozygous non-white cat, all offspring will be heterozygous white.

• If two heterozygous white cats mate, there will be homozygous white, heterozygous white, and homozygous non-white offspring in a ratio of 1:2:1. The ratio of white to non-white offspring is 3:1. If a heterozygous white cat mates with a homozygous non-white cat, there will be both heterozygous white and homozygous non-white offspring in a 1:1 ratio.

• If two homozygous non-white cats mate, all offspring will be homozygous non-white. Homozygous non-white cats are therefore true-breeding for non-white when co-bred.

• Geneticists differentiate between what a cat is genetically versus what it looks like by defining its genotype versus its phenotype. A homozygous white cat has a white genotype and a white phenotype. Likewise, a homozygous non-white cat has a non-white genotype and a non-white phenotype. A heterozygous white cat, on the other hand, has both a white genotype and a non-white genotype, but only a white phenotype.
  

That's enough of that; let's move on to something more challenging.

The Main Genes of Silver and Gold Persians

A = Agouti and is the ground-color of tabby; hairs banded yellow/orange.
B = Black pigment
D = Dense pigmentation
d = Dilute pigmentation (eg: black to blue)
I = Inhibitor gene. Suppression of pigmentation from parts of hairs
i = Normal pigmentation. Full development of pigmentation.

Genotypes of Silver and Gold Persians

A-B-D-I- = Chinchilla Silver, Shaded Silver, and Silver Tabby
A-B-ddI- = Blue Chinchilla, Blue Shaded, Blue Silver Tabby
A-B-D-ii- = Chinchilla Golden, Shaded Golden

The Main Genes of Silver Persians

The hairs in silver Persians are tipped with color. The depth of the tipping distinguishes a cat as either chinchilla or shaded, the chinchilla having the lightest tipping.

The gene all cats of the silver group possess is termed the inhibitor, symbolized I. The I gene is dominant, and its effect is to supress the development of pigment (coloring matter), particularly in the more lightly pigmented areas of the animal's coat. In the 'wild' type cat - the tabby - these are of course the agouti areas between the dark blotches or stripes, and also the under-color towards the roots of the hairs.

If the effect of the gene is limited, the result in a good exhibition animal is an intense black tabby pattern on an almost white ground-color. This is the silver tabby, which can come in mackerel or classic. The intense coloring is partly the result of generations of selective breeding. Selective breeding can also disperse and weaken the tabby pattern, however, and magnify the expression of the inhibitor gene. The result is to drive the last remaining pigment to the tips of the hairs, so that the cat looks white to a casual glance. But it has the characteristic sparkle of the chinchilla.

Between the extremes of the silver tabby and chinchilla is the shaded silver with abundant hair tipping giving the appearance of wearing a color mantle. These cats are commonly produced by mating silver tabbies to chinchillas. The amount of tipping varies widely - from that of a poorly-defined silver tabby to a dark chinchilla.

The silver tabby, shaded silver, and chinchilla all have an identical color genotype (genetic make-up), the degree of pigmentation depending on modifying polygenes.

The Main Genes of Golds

Golden cats show a very similar coat pattern to those described above, with dark tipping or shading. However, the undercoat is a rich, warm cream rather than white, and when combined with black tipping the 'golden' appearance results.

The different undercoat betrays a fundamental genetic difference from cats of the silver group: Golds do not have the inhibitor gene. Instead, they seem to have a gene or group of polygenes that simply increases the amount of yellow pigment in the agouti hairs. Without the effect of the inhibitor gene, however, the color tipping is generally heavier than in corresponding silver cats.

Some may use the word "smeared" or "edged" in place of "tipped", because without the influence of the inhibitor gene, it simply isn't accurate. But most breeders use the word "tipped" anyway, because it's just easier to imagine and further explanation isn't required.

Of course, breeders of chinchilla and shaded silvers have to select for the desired degree of tipping, and the same polygenes are probably involved here. In fact, golds occur in litters with silver offspring if the parents are not homozygous for the inhibitor gene.

Now that we have moved into the era of Blue Gold and Blue Silver, an entirely new alchemy exists. These wonders of nature have all of the sparkling qualities of the traditional Silvers and Golds, but instead of being tipped with black, they are tipped in blue. This gives the Blue Silver and softer, more pastel look, and the Blue Golds an ethereal appearance that can only be truly appreciated in person. The combination of the warm hues of pale cream tipped with the cool tones of pale blue unite to create one of the most exquisite coat colors possible.

The Main Genes of Smoke Persians

A = Agouti and is the ground-color of tabby; hairs banded yellow/orange
a = Non-agouti and is hair that is not banded; unicolored (acts only on black/brown)
B = Black pigment
b = Brown (chocolate or chestnut) pigment
C = full-color, or maximum pigmentation
D = Dense pigmentation
d = Dilute pigmentation (eg: black to blue)
I = Inhibitor gene. Suppression of pigmentation from parts of hairs
i = Normal pigmentation. Full development of pigmentation
O = Orange, or all pigment turned to yellow/orange
o = Normal pigmentation (not orange)

The hairs in smoke Persians are tipped with color. The depth of the tipping distinguishes a cat as either shell, shaded, or smoke. A Shell has the lightest tipping and is recognized by CFA in only two colors which are red (Shell Cameo) and tortoiseshell (Shell Tortie). The next darkest color is the Shaded group and again only the reds and torties are recognized by CFA (Shaded Cameo and Shaded Tortie). The darkest in the group are the Smokes with most of the hair being colored. Smokes are recognized by CFA in all colors which include black, red, blue, cream, blue/cream, and tortie. Smokes are the most common coloring while the shaded and shell are more rare. Smokes are also being bred with bi-colors to produce bi-colored smokes (bi-colors are those cats with the spotting gene that produce cats with patches of white such as the calico).

Genotypes of tipped colors

aaB-D-I- = Black Smoke
aaB-ddI- = Blue Smoke
D-I-O(O) = Shell Cameo, Shaded Cameo, Smoke Cameo (Red Smoke)
ddI-OO = Cream Smoke Cameo
D-I-Oo = Shaded Tortoiseshell, Smoke Tortoiseshell
ddI-Oo = Dilute Smoke Tortiseshell (Blue/Cream Smoke)

As a note of comparison, the geneotype for a solid black cat is: aaB-C-D-. Note the only difference between a solid black cat and a black smoke is the I or Inhibitor and the C or Full color genes. The best-known smoke is the black, and it is due (as are all smokes) to the combined action of the Inhibitor gene and the non-agouti a. The I gene produces a white undercoat, but the a gene produces extra amounts of pigment. The result is profuse tipping, but modifiers can increase or decrease the tipping to the extent that some smokes are almost indistinguishable from solid colored cats and others are very pale. The long-haired smoke with just the right amount of tipping and undercoat is undoubtedly a magnificent cat.

The cameos are the red equivalent of black smokes. The result from combining the I gene with the orange O. These too are beautiful cats, possessing a white undercoat and an overlay of rich apricot to red tipping.

There are three varieties in smokes, corresponding to the three degrees of tipping. The palest is the shell cameo which has a delicate sprinkling of red tipping. Next is the shaded cameo which has a slightly darker red appearance. Darkest is the smoke cameo in which the undercoat is white and the veiling is ideally a deep, even red. As with all red cats, however, tabby marking are inherent and can be dispersed only by selective breeding. This is because the non-agoutie gene is ineffective on orange pigment, and for this reason too the smoke cameo - unlike other smokes - owes its intensity of color only to polygenes and selective breeding, not to a non-agouti geneotype. When tabby markings are allowed to remain, the result is the cameo tabby, with red markings on a white background.

A very elegant series of cats are the blue smokes and cream cameos, produced by introducing the dilution gene d. These are clearly of smoke form, as shown by their white undercoat, but the tipping is now cream or blue. There is considerable variation in the cream tone, from warm cream to an exquisite pale shade that has the slightest hint of pink, due to the action of polygenes. You can also get a poor quality cream that has a flat "brown paper bag" look. This is why it is important to not only breed for "type" and personality, but breed for favorable color factors.

The dilute smokes are the least often bred colors because of the complicated color factors and most importantly, the difficulty most breeders have in determining whether a kitten is a smoke or a solid. The "clown" markings can be difficult to see because of the pale coat color (for more information on how to tell if you have a smoke or a solid kitten, see the page on determining factors).

The following chart is a basic guide for combining the red and black genes. When figuring for dilutes you must take that gene into consideration as well as any dilute carriers. Factor into that the smoke gene, and you can see just how complicated breeding smokes can be!

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