Basic Savannah Colour Genetics

Basic Savannah Colour Genetics

Many breeders shudder at the thought of unraveling the genetic codes behind their cats’ colour and pattern, and little wonder.  Open a textbook on cat colour genetics and your mind swims with various arrays of letters whose secrets can only be unlocked by the most advanced cryptographer, or so it seems.  Fortunately, it’s not as hard to understand as you think.  The Savannah breed has a relatively small number of accepted colours/patterns:  Brown(Black) Spotted tabby, Melanistic (Solid Black), Silver(Black) Spotted Tabby, and Black Smoke (Solid Silver).  This article will only be covering those four permissible colours/patterns, so you won’t see an outline of the non-permissible colours/patterns that can crop up in our breed.

Genes and Alleles

A gene is a point on a chromosome that determines many different things.  For purposes of this article, we are dealing with colour and pattern genes.  Each cat has a pair of genes; one from each parent.  To describe these genes, we use 2 letters.  A capital letter signifies a dominant gene, and a lower case letter signifies a recessive gene. 

An allele is a variation or mutation of the original gene.  For example, the Agouti gene “A” has a variation allele for Solid or Non-agouti “a”.  In layman’s terms, the word gene and allele often mean the same thing, though technically there is a subtle difference.

Dominance

No, this doesn’t refer to a lady with a whip and stilettos.  Dominance refers to a gene that masks or overpowers other genetic colours or patterns.  Dealing with dominant colour/pattern genes with regards to a breeding program is very easy, for one simple fact:  If you can’t see it, it isn’t there.  So, if a colour/pattern that you want to avoid in your breeding program happens to be a dominant colour/pattern gene, all you have to do is avoid breeding those cats that visibly show the colour/pattern.  In our Savannahs, we have two dominant genes:  Silver (which controls colour expression) and Agouti (which is the tabby pattern).  A cat with a dominant colour/pattern can either carry both copies of the dominant gene, or it can carry one dominant and one recessive gene.

Recessives

Recessives are the Ninjas of the genetic world.  They are sneaky, are often hidden, and they can pop up when you least expect them.  Ironically, our recessive alleles are Melanistic (Solid Black) and Black Smoke (Solid Silver).  Many of the non-standard colours/patterns in our breed are recessives, which makes it very difficult to cull from our programs.  A recessive can be present in dominant colour/patterns for endless generations, and there is no way to know it is there just by looking at the cat.  In order for a recessive to appear, both parents must carry it.  Also, for a cat to display the recessive colour/pattern, it must carry both copies of the recessive allele.

Luckily, you can DNA test for our permissible recessives (non-silver and non-agouti), and many of the non-permissable colours/patterns that are present in the Savannah breed.

Homozygous & Heterozygous

As mentioned, each cat has two copies of each gene.  When both copies are the same, we call this Homozygous.  When each copy of the gene is different, we call this Heterozygous.  Usually heterozygous cats have one dominant and one recessive allele.

Permissible Savannah colours/patterns defined

Now that we have covered the basic terminology, it’s time to take a more detailed look at our permissible Savannah colours/patterns.  There are dozens of different genes that affect the colours and patterns in our savannahs, even amongst our four permissible colours.  However, we will only be dealing with two genes in this article:  The Agouti gene and the Silver gene.  Each of our cats has a variation of both of these genes, regardless of whether they are Brown(Black) Spotted, Melanistic, Silver(Black) Spotted or Black Smoke.  Therefore, the Agouti and Silver genes are at the very core of our Savannahs’ colour/pattern.

Silver – “I”

Silver is not actually a colour, but rather a gene that inhibits pigmentation of hairs.  It has a greater ability to suppress the warmer colours (phaeomelanin), such as reds or yellows, than the cool dark colours (eumelanin), such as dark brown and black.  The Silver gene creates a hair that is white at the base, and dark at the tip.  There is great variation in shades of silver, from very dark to almost white.  This depends on the length of the white and dark band on each hair.

Silver is dominant to the Non-silver (brown or golden in savannahs) allele.  So our cats, even if they are Brown(Black) Spotted Tabbies or Melanistics, have one form of this gene.  They are either Silver or Non-silver.

The Silver gene is “I” and the Non-silver allele is “i”.

Agouti – “A”

The Agouti gene is rather complex but I will try to make this as simple and easy to understand as possible.  In layman’s terms, Agouti is the Tabby gene.  This covers ticked tabby, classic (marble) tabby, mackerel tabby, and spotted tabby.

This gene controls how colour is deposited on the hair via the Agouti protein, which gives the fur its ticked appearance and creates a hair that is black at the tip, and yellow at the base.  This produces the ticked tabby, as seen on the Abyssinian.  For the other forms of tabby, there is a secondary system of pigmentation that produces dark or black hairs with no or minimal ticking at various points on the skin.  However, they are all considered Agouti.  With regards to Savannahs, both the Brown(Black) Spotted and Silver(Black) Spotted Tabbies are “Agouti”.

In addition to Agouti, there is the recessive allele “Non-agouti” or Solid.  In these cats, the protein responsible for the bands or ticking on the hair shaft is defective, but the underlying tabby pattern (spotted in savannahs) is still present.  This produces a hair that is all one colour, so it is solid.  The solid colours accepted in the Savannah are Melanistic (Solid black) and Black Smoke (Solid Silver).

So, all our cats have one form of this gene, whether they are Tabby (Agouti) or Solid (Non-agouti).

The Agouti gene is “A” and the Non-agouti allele is “a”.

The Wide-band gene

I felt it important to at least make mention of the wide band gene, since it is covered in Robinson’s Genetics.  This gene does not have any concrete scientific evidence to support or detail it, but there are several theories.  The effect of this gene (or genes) is that it widens the yellowish band on the hair, making for a very small amount of black pigment in the tip, and a clear golden ground colour.  It has been theorized that the cause of this could be a single dominant (complete or incomplete) gene, or that the maximized agouti protein production is the result of polygenic (more than one gene) factors.

The Codes

Visually, we have four permissible colours for our Savannahs.  Genetically, there are nine variations.  What a cat can produce has to do with the genes they carry, as well as the genes of the mate.

AAii

This is a Brown(Black) Spotted Tabby that does not carry the Solid allele.  This cat can produce Brown(Black) Spotted Tabbies and Silver(Black) Spotted Tabbies.

Aaii

This is a Brown(Black) Spotted Tabby that carries the Solid allele.  This cat can produce Brown(Black) Spotted Tabbies, Silver(Black) Spotted Tabbies, Melanistic and Black Smoke.

aaii

This is a Melanistic (Solid Black).  This cat can produce Brown(Black) Spotted Tabbies, Silver(Black) Spotted Tabbies, Melanistic and Black Smoke.

AAII

This is a Silver(Black) Spotted Tabby that does not carry the Solid allele or the Non-silver allele.  This cat can only produce Silver(Black) Spotted Tabbies, regardless of what other permissible colour/pattern it is bred to.

AaII

This is a Silver(Black) Spotted Tabby that carries the Solid allele but not the Non-silver allele.  This cat can produce Silver(Black) Spotted Tabbies and Black Smoke.

AaIi

This is a Silver(Black) Spotted Tabby that carries the Solid allele and the Non-silver allele.  This cat can produce Brown(Black) Spotted Tabbies, Silver(Black) Spotted Tabbies, Melanistic and Black Smoke.

AAIi

This is a Silver(Black) Spotted Tabby that carries the Non-silver allele but not the Solid allele. This cat can produce Silver(Black) Spotted Tabbies and Brown (Black) Spotted Tabbies.

aaII

This is a Black Smoke that does not carry the Non-silver allele.  This cat can produce Silver(Black) Spotted Tabbies and Black Smoke.

aaIi

This is a Black Smoke that carries the Non-silver allele.  This cat can produce Brown(Black) Spotted Tabbies, Silver(Black) Spotted Tabbies, Melanistic and Black Smoke.

What will I get?

Here is a chart showing all nine of the above mentioned cats bred to each other.  Keep in mind the percentages shown are not always the percentage of the kittens in the litter that will have this colour.  Usually it does work out this way, but the genetic dice is rolled for each kitten.  It all depends on what genes the egg and the sperm is carrying.  You could have a 50% chance of getting Brown(Black) Spotted Tabbies or Silver(Black) Spotted Tabbies, yet have the entire litter made up of all one colour.

I have colour coded the chart to make it easier to understand at a glance.

A = Tabby

a = Solid

I = Silver

i = Non-silver

Breeding with colour in mind

There are several different ways you can group our permissible colours together.

Agouti Group 

Brown(Black) Spotted – AAii & Aaii

Silver(Black) Spotted – AAII, AaII, AAIi, & AaIi

Solid Group

Melanistic – aaii

Black Smoke – aaIi & aaII

Silver Group

Silver(Black) Spotted – AAII, AaII, AAIi, & AaIi

Black Smoke – aaIi & aaII

Non-silver Group

Brown(Black) Spotted – AAii & Aaii

Melanistic – aaii

Brown(Black) Spotted Program

By far, the most popular savannah is the Brown(Black) Spotted Tabby.  Whether you are interested in the Golden or Cool-coloured cats, they are both Non-silver Agouti cats.  If you are looking to produce only Brown(Black) Spotted Tabbies, and have no interest in either Silvers or Solids, there is only one genetic code that you will want: AAii.  Excluding Silver is very easy to do; just don’t breed any Silver cats.  Silver is dominant, so if you don’t see it, it’s not there.  Excluding Solid is a bit trickier.  Solid (Non-agouti) is a recessive, so your beautiful Brown(Black) Spotted Tabby can carry it, and you’d never know by looking at him/her. 

The only way to know for certain if your Brown(Black) Spotted Tabby carries Solid is to DNA test, although, if one of the parents is a Solid then it’s 100% that the cat carries Solid.  Also, if one of the littermates is Solid, there is a high chance the cat carries Solid as well.  If you breed a Brown(Black) Spotted Tabby that carries solid to a Brown(Black) Spotted Tabby that does not, you will still only get Brown(Black) Spotted Tabbies, however some will carry solid. 

If you are a purist, and want only Homozygous Brown(Black) Spotted Tabbies, then be sure to DNA test any kittens that you plan to use in your breeding program.

Brown(Black) Spotted & Melanistic Program

There are two types of breeders that have these programs:  Ones that want to produce Melanistics along with their Brown(Black) Spotted Tabbies, and ones that don’t mind if they happen to pop up. 

If you want to produce Melanistics, your Brown(Black) Spotted Tabbies will need to carry for Solid, or you won’t see any Melanistics at all, even if one of the parents is Melanistic.  However, if you have a Brown(Black) Spotted Tabby that does not carry Solid, breeding it to a Melanistic will result in 100% Brown(Black) Spotted Tabbies that carry the Solid allele.

If you want to have quite a few Melanistics produced, you will likely want at least one Melanistic cat in your program.  If your stud is Melanistic, you’ll produce more than if your Melanistic is a queen, simply because a stud can produce far more kittens in his career that a single queen.  And if you want lots of little black panthers, you can always breed Melanistic to Melanistic and get 100% Melanistic kittens.

You can also produce Melanistics if you only have Brown(Black) Spotted Tabbies that all carry for Solid (Melanistic is the Solid form of Brown(Black) Spotted Tabby).  These cats bred together will produce approximately 25% Melanistic and 75% Brown(Black) Spotted Tabbies.  Of course, each of these pairings (except Melanistic to Melanistic) will produce Brown(Black) Spotted Tabbies.

Silver (Black) Spotted Program

This is pretty much the same idea as a Brown(Black) Spotted program, except that you have two recessives to think about instead of just one: the Solid allele and the non-silver allele. 

Ideally, you want to breed Homozygous Silvers only (AAII or AaII), as the non-silver allele is most commonly thought to be the cause of tarnishing, although it may be possible for any Silver to display tarnishing.  (Tarnishing is the expression of brown colouring at the extremities of a Silver cat, such as nose, paws, ears and along the back.) There are several theories regarding exactly how tarnishing is created.  For those seriously considering a Silver program, it is very important to research as much information as possible regarding tarnishing and how to avoid it.

If you do not wish to produce Black Smokes, you will want to avoid Silvers that carry for Solid. 

Keep in mind that you can still utilize cats carrying any recessive, and by the use of DNA testing, you can breed the recessives out of your lines.

Copyright Anatole Cannon 2010

Not to be published, whole or in part, without permission.