Genetics of the silver and golden Persians is relatively simple with a basic knowledge of how genes work, and in particular, the specific genes that are responsible for making a silver/golden Persian look the way they do. Genes are encoded on DNA which can be found in almost every cell and are the blueprints to making a living organism. They ultimately determine what we see when we look at a living creature. The physical appearance is known as the phenotype of an organism and the genetic make-up is known as the genotype.

There are multiple alleles, or different types of each gene, that can contribute to a genotype. Genes can be dominant, which means if they are present, they prevail in the resulting phenotype and we see the gene's expression. Genes can also be recessive meaning that if a dominant allele for the same gene is present, then you will not see the recessive gene in the phenotype as it yields to the dominant gene. All mammals have two copies of each gene -- one obtained from the mother and one from the father. Hence, a genotype could be what is termed homozygous dominant, heterozygous, or homozygous recessive for any gene. Homozygous dominant means that the animal inherited the dominant allele for a gene from both parents. Heterozygous means it inherited both a dominant and a recessive allele for the same gene, one from the mother and one from the father. Obviously, we would only see the dominant gene in the resulting phenotype, but we would say that the animal is "carrying" the other gene as it has the genetic ability to produce the recessive gene it is carrying if paired with an individual that also has that recessive gene. Homozygous recessive means that the animal inherited the recessive allele for a particular gene from both parents. The phenotype is a result of the genotype within, so it is here that we will begin our endeavor into silver and golden genetics.

Genotypes
The silver genotype is denoted by the dominant inhibitor gene, I, the dominant agouti gene, A, as well as wide-band polygenes (which are thought to have variable penetrance and can express themselves in some cats more than others), Wb: I- A- Wb-. A silver or golden is, by nature, a black cat with the color restricted, or in this case, inhibited to the ends of the coat. All silver and golden Persians are agouti cats -- meaning they are genetically tabbies and appear as such at birth. A non-agouti silver would be a black smoke or shaded black -- aaI- -- depending on the amount of overall tipping. Due to this recessive non-agouti gene causing the black smoke or shaded black coloration, it is unlikely to get black smokes or shaded blacks in colorbred silver breedings since both silvers would have to be carrying the recessive allele for non-agouti, a, and silvers have been selectively bred over the years to be dominant for the Agouti gene. Although smoke and shaded colors are quite probable in noncolorbred breedings, as discussed below.

A 5-week old shaded black kitten (non-agouti silver) produced from two light shaded silver parents five generations away from any solids. The lack of barring, extremely dark coloration, and a solid black nose are significant indicators that he is non-agouti.1

A chinchilla silver is thought to have more wide-band gene expression than a shaded silver, although both are thought to have a strong to medium wide-band effect (remember it has variable penetrance). The wide-band polygenes are responsible for widening the agouti band on the hairs and making the tabby pattern of the agouti cat less distinct and blurred. A silver or golden without the wide-band effect has a distinct tabby pattern and is known as the silver or golden/brown tabby.

A very strong wide-band effect on this gorgeous chinchilla silver female. 2

This beautiful shaded silver female has excellent even shading. 3

A golden results from a homozygous recessive inhibitor gene and dominant agouti gene with a strong to medium wide-band effect: ii-A-Wb. There is no such thing as a "golden gene". Breeders refer to it because it is easier to say and understand than the actual genotype that is going on. Unlike silvers, goldens have a recessive inhibitor gene, as do solids, tabbies, etc. A golden is a wide-band black tabby (known as brown tabby in the United States) with a recessive inhibitor gene. The clarity of the ground color of the golden will be determined from the wide-band polygenes. Take note that a golden Persian has nearly the same genotype as a brown tabby Persian. It is only through selective breeding to clarify the coat and intensify the ground color that the golden Persian has become a distinct color class of its own. Polygenes are thought to contribute to the overall warm golden appearance but a strong wide-band effect is essential for a golden Persian. Otherwise, there is little to distinguish a golden from a brown tabby which is why one should use great caution in breeding his or her golden Persians to noncolorbred lines -- that is, lines that are known not to have a strong wide-band polygenes, i.e., solid, smoke or any other color of Persian besides silver or golden. Remember if a strong wide-band effect has not been selectively bred for, it is safe to assume a cat does not have the necessary alleles on the many genes that give the strong wide-band effect. A golden or brown tabby is an agouti cat with very low to no expression of the wide-band polygenes and a recessive inhibitor gene. Genetically they are almost very much the same, which is probably why golden tabbies have never been accepted for championship status in CFA.

A bright apricot chinchilla golden has the strongest wide-band effect whereas a darker, more barred brown-colored golden has the weakest in the golden color class. If your desire is to breed for the bright apricot chinchilla golden, the only way to get strong wide-band polygenes, other than by multiple random mutations, is to selectively breed for it.

A chinchilla golden with a strong wide-band effect. Five generations from any solid influence.4

Probabilities using Punnett Squares
Colorbred silvers and goldens follow a simple Punnett Square cross of the inhibitor gene to determine the probability of colors in the first generation. A dominant silver, II, or a silver that does not "carry gold", will produce all silvers when bred to a silver carrying gold, Ii, or a golden Persian, ii. Since an animal receives two copies of each gene upon conception, one from the mother and one from the father, then a kitten from a homozygous dominant silver would have to have inherited at least one dominant inhibitor gene, I. Remember if a dominant allele is present, then that is what is expressed in the phenotype. Sex of the cat is not important for inheritance of the inhibitor gene as it is a somatic gene meaning it does not reside on a sex chromosome, X or Y. Bred to a heterozygous silver, or Ii, 50% of the kittens would be homozygous dominant, II, or not carry gold, and 50% would be heterozygous, Ii, or carry gold. One can easily visualize this by creating a Punnett Square as shown in figure 1.

Figure 1: A homozygous dominant silver bred to a heterozygous silver (silver carrying gold) will produce 50% II (homozygous dominant silvers) and 50% Ii offspring (heterozygous silvers carrying gold).

Bred to a golden, a homozygous dominant silver would produce 100% silvers carrying golden, or Ii (see figure 2).

Figure 2: A homozygous dominant silver bred to a golden will produce 100% Ii, silvers carrying gold.

A silver carrying golden, or Ii, would produce 50% silvers carrying golden, Ii, and 50% goldens, ii, when bred to a golden, ii. See Punnett Square figure 3.

Figure 3: A heterozygous silver (silver carrying gold) bred to a a golden will produce 50% Ii (silver carrying gold) and 50% ii (goldens).

Bred to another silver carrying golden, Ii, would produce 25% homozygous dominant silvers, II, 50% silvers carrying golden, Ii, and 25% goldens, ii (see figure 4).

Figure 4: A heterozygous silver (silver carrying gold) bred to another heterozygous silver will produce 25% II, homozygous dominant silvers, 50% Ii, heterozygous silvers, and 25% ii, goldens.

Last, but not least of our colorbred breedings, a golden bred to a golden would produce 100% goldens (see figure 5). Homozygous recessive Persians for the inhibitor gene can only produce homozygous recessive, therefore silvers cannot be produced in a golden to golden breeding.

Figure 5: A golden bred to a golden will produce 100% ii, goldens.

Non-Colorbreeding
Outcrossing to solids can lead to many unique situations. Remember silvers are genetically black cats so outcrossing to any other color than black can produce different colors of kittens. The color gene is carried on the X chromosome so the sex of the cat one is outcrossing the silver to is also important. A female carries two X chromosomes, one from her mother and one from her father. A male carries an X chromosome from his mother and a Y chromosome from his father. Only males have the Y chromosome and for this reason they only have one X chromosome. Since a male has only one X chromosome, he only has one allele per gene. Therefore, any gene that is found on X, whether dominant or recessive, will be expressed in the phenotype of a male (this is why X-linked traits such as color-blindness and hemophilia in humans are more prevalent in men than women). Therefore, males inherit their coat color from their mothers, whereas females inherit it from both mom and dad (remember this does not include color modifier genes such as the inhibitor or agouti genes -- this is strictly the genetic color of the cat -- black or red).

The color gene is unique in that there are two dominant colors -- black and red. If a female inherits an X chromosome with the black color gene from one parent and an X chromosome with the red color gene from another parent, then she will be tortieshell meaning she will have splotches of black and red throughout her coat. A homozygous dominant silver female (AA,II) bred to a red male (cameo, red, cream, flame-point, etc) would produce tortie silver females and (black) silver males (see figure 6). If the silver female carries gold (Ii) then another whole array of colors is possible including brown and brown-patched tabbies. If she carried golden and non-agouti, solids and parti-colors are also a possibility (see figure 8 for more details).

Figure 6: A silver female bred to a red male (cameo, flame-point, solid red, red tabby, cream, etc.) will produce 50% tortie/torbie colored females and 50% black colored males.

Now of course it gets more complicated than this. If the female carries non-agouti, then one could also get shell/shaded or smoke tortieshell females and black shell/shaded or smoke males in addition to the above. Non-agouti cats are NOT silvers!  A silver is defined by 2 genes -- the inhibitor gene AND the agouti gene.  If a cat only has the inhibitor gene, but is nonagouti, it is a shell/shaded/smoke and belongs in the shaded and smoke division.  A cat that has the inhibitor gene and the agouti gene, on the other hand, is a silver; it is important to remember that not all colors of silvers are accepted for show in CFA.  For example, the silver torbies or dilute silvers and goldens are accepted for registration in CFA, but are not accepted for show.

If both cats carried dilute, you can also add the possibility of the dilute of red and black to the offspring -- shaded or smoke blue-cream females and shaded or smoke blue males. I must also mention that if your silver female carried the color point gene as well as your red male, then one could get Himalayan patterns in the above colors.

A Shaded-silver point. Notice the shading is limited to the extremities and characteristic blue Himalayan eyecolor. 6

A shaded torbie-silver. Patches of red tipping evenly mixed with the black. A torbie will exhibit black nose liner on a pink/red nose, and characteristic tabby markings in the coat such as faint barring on the legs and a M on the forehead.  7

On the other hand, a homozygous dominant silver male bred to a red female (cameo, red, cream, flame-point, etc.) will produce torbie silver females and red agouti cameo males (figure 7). Males cannot be tortieshell since they only have one X chromosome. If your silver again carried golden (Ii) or non-agouti (Aa) then you can add brown-patched tabby females and red tabby males, or solid tortie females and solid red males, respectively, to the above colors.

Figure 7: A red female bred to a black male will produce 100% tortie females and 100% red males.

As stated earlier, it is common for noncolorbred breedings to occasionally produce smokes and non-agouti shadeds/shells (shaded and smoke division). A noncolorbred silver is typically heterozygous for the agouti gene (Aa) as solids and other non-tabby colors of Persians are typically non-agouti -- homozygous recessive, aa. There are numerous noncolorbred crosses one could do so I have compiled a list of some of the more common silver combinations in Figure 8.

Dilute Gene
The dilute gene is an important factor one needs to consider when noncolorbreeding. The blue-silver and the blue-golden are the products of two recessive dilute genes added to the silver and golden genotypes. When a cat is homozygous recessive for the dilute gene, a black colored cat will appear blue and a red colored cat will appear cream. A blue-silver or blue-golden looks like a normal black silver or golden in every respect except the tipping will be blue instead of black and the nose leather will be an old rose instead of brick red. The liner and paw pads will also be a bluish-gray rather than the rich black. The dilute gene is recessive, dd, so it can be carried for many generations before showing in the phenotype. Blue-silvers and blue-goldens are currently not accepted for show in CFA so these colors are seldom bred for in the silver/golden fancy. However, they are possible when one outcrosses their silvers or goldens to solid or other colors of Persians.

Table of Crosses and Resulting Color Offspring for Common Colors used in a Silver/Golden Breeding Program.

Figure 8: This table does not take dilute genes or sex of the parents into account. If both parents carry a dilute gene, add the dilute of black (blue) and red (cream) to the above colors.

* Very Rare ** Only if silver/golden carries non-agouti, Aa (typically if they are noncolorbred)

About the cats pictured:

1: SimbaKui Shaded Black Kitten
2: GC RW Scrimshaw Star Safire -- Chinchilla Silver
3: GC Shadedknoll Cherish -- Shaded Silver
4: SimbaKui All That Glitters is Gold of L'Ainulindale -- Chinchilla Golden Kitten
6: Falabella's Tara -- Shaded Silver Point
7: Jemapelle Shaded Tortie Kitten