Dinner Table Analysis
of Color Genetics

The simple kind of genetics is called Mendelian because a man named Mendel did a lot of tests involving controlled breeding of flowers. He found that Red flowers crossed with Red flowers produced Red flowers and that yellow flowers crossed with yellow flowers produced yellow flowers, too.

So, let's create a table:

Chart 1	Red (Pollen)
Red (flower)	Red (Seeds) (seeds grow to be red flowers)

and

Chart 2	yellow (Pollen)
yellow (flower)	yellow (Seeds) (seeds grow to be yellow flowers)

and

Chart 3	yellow (Pollen)
Red (flower)	Red* (Seeds) (seeds grow to be red flowers)

Mendel was surprised that red flowers crossed with yellow flowers produced red flowers. Always.

Notice that the seeds, the offspring, that produced red flowers, even though they came from a yellow flower, are marked with a "*". Combining the four results into one table, you get:

Chart 4	Red (Pollen)	yellow (Pollen)
Red (flower)	Red (Seeds)	Red* (Seeds)
yellow (flower)	Red* (Seeds)	yellow (Seeds)

This shows what a dominant gene does. If either parent has one, the offspring have that trait.

Next, Mendel crossed his Red* flowers with other Red* flowers and gave the Red* flowers the name "hybrid" which today includes any mixed genetics, not just color. He got another surprise!

Chart 5	Red* (Pollen)
Red* (flower)	3/4 Red	1/4 yellow

Through a truly exhausting amount of work spanning several years and many, many generations of the flowers, he proposed the following:

Chart 6	RR	yy
RR	RR	Ry
yy	Ry	yy

which is the Chart 4, with a new notation. By convention, lowercase letters are used for recessive traits, upper case letters are for dominant traits.

In this example, the Red is dominant because it always shows. The yellow is recessive because a flower can carry it, and pass the trait to its offspring.

Redrawing chart 5 would produce:

Chart 7	Ry
Ry	RR	Ry
	Ry	yy

where Chart 5 shows the phenotype & Chart 7 shows the genotype of the flowers.

So, in summary: we have an overview of how Mendel made this up, we have defined dominant, recessive and carried genes, and we have used these tables to show possible offspring. This is the type of table commonly used for mating charts for cats.

For our flowers:

Chart 8	RR	Ry		yy
RR	RR	RR - 1/2		Ry
		Ry - 1/2
Ry	RR - 1/2	RR - 1/4	Ry - 1/4	Ry - 1/2
	Ry - 1/2	Ry - 1/4	yy - 1/4	yy
yy	Ry	Ry - 1/2		yy
		yy - 1/2

We'll see how the numbers get there, too. Note that in the middle box, Ry crossed with Ry, there are 1/4 RR, 1/2 Ry and 1/4 yy offspring.

Often, mating charts are presented like this:

Table 1-a	RR male
RR female	100% RR offspring
Ry female	50% RR offspring	50% Ry offspring
yy female	100% Ry offspring

Table 1-b	Ry male
RR female	50% RR offspring		50% Ry offspring
Ry female	25% RR offspring	50% Ry offspring		25% yy offspring
yy female	50% Ry offspring		50% yy offspring

Table 1-c	yy male
RR female	100% Ry offspring
Ry female	50% Ry offspring	50% yy offspring
yy female	100% yy offspring

You can compare this list of male/female combinations (I've used the flower genetics as an example) to Chart 8 and see that it has the same information.

Okay, as promised, the explanation of where the numbers come from. I am still using the simpler flower genetics because all of this is still general stuff, not specific to cats. I'll switch colors again for that. Also, I used the above notation because it is most likely what others use. I have developed a slightly different one because it shows how easy the numbers are. On this flower sample, you'll see mine is clumsy, but when we switch over to cat genetics, I think you'll see that my method is easier.

Using the example, an Ry X Ry mating (Chart 5) could be shown like this:

Chart 9		male or pollen gives offspring:
		R	y
female or flower gives offspring:	R	RR	Ry
	y	Ry	yy
(each parent gives offspring one of its two genes)

Possible offspring are:

• 1/4 have R from each parent
• 1/4 have R from mom, y from dad
• 1/4 have y from mom, R from dad
• 1/4 have y from each parent

That's what Mendel tried to figure out with Chart 4. That's how the numbers were filled in on Chart 8. That's how mating charts like Table 1 are made.

All of the work up to here can be developed by expanding Chart 9.

Okay, now to the fun stuff ... feline genetics.

I'm going to write only about coat color, and primarily about genetics as relevant to Burmese.

First, the basics. One of the best examples of an "ordinary" cat is a brown-and-black striped "alley cat." This coat pattern is known as a brown mackeral tabby.

By convention, genes are represented by letters; uppercase is dominant, lowercase is recessive. Each letter stands for the kind of gene it represents. So, we'll start with a discussion on coat type. And, remember, all genes come in pairs, one from the sire, one from the dam.

As it turns out, the tabby markings on the alley cat are dominant, notated C_T, the solid of a black cat is recessive, notated c for solid color. Also, it is possible to replace one or both of the "coat pattern" genes in the Siamese pattern (c_S) and Burmese pattern (c_B). A cat could have two solid color genes: cc (like a black cat) or, C_TC_T (two tabby pattern genes) or, c_Sc_S (two Siamese pattern genes) or, c_Bc_B (two Burmese pattern genes).

If the cat has one C_T gene and one c_B gene, it will look like a striped tabby, and is said to carry the Burmese pattern gene, because the tabby gene is dominant.

But, now it gets more complicated than the flower example, because there are more than two possibilities (R and y). Suppose some black cat (cc) mates with a Siamese (c_Sc_S)? It turns out that the solid dominates and you get black solid kittens carrying the Siamese gene (cc_S). Similarly, this same black cat (cc) mated to a Burmese (c_Bc_B) produces solid black kittens carrying the Burmese pattern gene (cc_B). Notice that all the genes are lowercase because the tabby pattern, C_T, is dominant over them all. (I've left out the genetics of different types of tabby -- Burmese don't come in tabby.)

Then, we have the Tonkinese. The Tonkinese breed is descended from some crosses between some Burmese and some Siamese. Of interest is this: a Burmese (c_Bc_B) crossed with a Siamese (c_Sc_S) produces a litter of kittens (c_Bc_S) with the Tonkinese pattern. The genes are called half-dominant or semi-dominant because the Tonkinese pattern (c_Sc_B) is a blend or compromise between the Siamese pattern (c_Sc_S) and the Burmese pattern (c_Bc_B).

Notice that if you mate two Tonkinese (c_Bc_S), then you will get Burmese pattern and Siamese pattern kittens as well as the Tonkinese pattern. Chart 9 can then be shown as:

Chart 10		stud gives offspring:
		cB	cS
queen gives offspring	cB	cBcB Burmese	cBcS Tonkinese
	cS	cBcS Tonkinese	cScS Siamese
(each parent gives offspring one of its two genes)

That is the essence of what makes Burmese, Burmese, and Siamese, Siamese and Tonkinese, Tonkinese.

Now, we are ready to consider colors. Consider the following:

BROWN (-and-black) Tabby		BLACK (solid coat)
	and
SEAL POINT Siamese		SABLE Burmese

What they all have in common is the black (B) gene. At this point, I will leave the tabby behind, because there is no tabby in Siamese, Burmese or Tonkinese.

The Black gene (B) gives the black coat in a solid cat, it gives a sealpoint coat pattern in a Siamese and is gives a sable coat pattern in a Burmese.

The Brown gene (b) gives rise to Chocolate point Siamese and Chocolate (or Champagne) Burmese.

Now, we have to go back to our diagram. A Sable Burmese (BB) crosses with a chocolate Burmese (bb) and will produce all Sable kittens:

Chart 11	B	B
b	Bb	Bb
b	Bb	Bb

(All of the kittens are Sable carrying chocolate.)

If a queen from this litter is bred to a chocolate male, kittens will be half chocolate and half sable carrying chocolate:

Chart 12	b	b
B	Bb	Bb
b	bb	bb

Remember, we called all those genes (c, C_T, c_B, c_S) c-names because they determine the coat pattern. And, remember, each cat has exactly two of them. And, each Burmese cat has exactly two color genes (B for Black and b for brown). The Burmese also have exactly two of the d-name genes (D for Dark, d for dilute). Most books introduce the d-name genes first. This is because they were discovered first in felines. I introduce the chocolate (brown gene, b) first for two reasons. 1) Chocolate was accepted in Burmese registrations earlier, and 2) you can understand that "b" means "brown" instead of "blue".

So, a Burmese has two c-name genes, (the coat genes, c_Bc_B), two b-name genes (Black/brown color genes, BB, Bb or bb) and two d-name genes (the dark/dilute genes, DD, Dd or dd).

All my sable Burmese are dark. The dilute gene on either a solid color black cat or on a Burmese pattern black gene (Sable) cat looks blue (I have no idea why gray cats are called blue). And the Dark is dominant. So DD is a dark cat, Dd is a dark cat carrying the dilute gene and dd shows the dilute coloring. Among Burmese breeders, the dilute gene is sometimes called the blue gene, which adds to the confusion.

In summary, the Burmese coat pattern is from a c-name gene (c_B) which is recessive to solid color (c) and semi-dominant over Siamese coat pattern. The combination of c_Sc_B gives the Tonkinese coat pattern. All of these are recessive to the dominant pattern, the tabby (C_T). A Burmese cat, therefore, is known to have two c_B genes, one from each parent.

Recognized by the major U.S. cat registries are four color classes of Burmese. Genetically, these four coat colors are controlled by the d-name and the b-name genes: Dark, dilute, Black and brown (where uppercase is used to indicate the dominant gene).

• Sable Burmese has Dark (DD or Dd) and Black (BB or Bb genes).
  
• Chocolate or Champagne Burmese, has Dark (DD or Dd) & brown (bb) genes.
  
• Blue Burmese has dilute (dd) and Black (BB or Bb) genes.
  
• Lilac or Platinum Burmese has dilute (dd) and brown (bb) genes.
  

Of course, everything shown here is in my notation. More commonly, you will see a table with nine sections, one for each genetic combination of the stud. (Note: Darbie Marlin has published an easier to use format for this table -- see the hyperlink below.)

We can summarize this in one final chart for an arbitrary Burmese mating, when each parent will contribute one d-name and one b-name gene:

Chart 13
		BD		Bd		bD		bd
	BD		BBDD Sable		BBDd Sable w/Bl		BbDD Sable w/Ch		BbDd Sable w/BlCh*
	Bd		BBDd Sable w/Bl		BBdd Blue		BbDd Sable w/BlCh*		Bbdd Blue w/Ch
	bD		BbDD Sable w/Ch		BbDd Sable w/BlCh*		bbDD Choc		bbDd Choc w/Bl
	bd		BbDd Sable w/BlCh*		Bbdd Blue w/Ch		bbDd Choc w/Bl		bbdd Plat

(*This sable kitten is said to carry both blue and chocolate.)

Also, it is important to remember that the British registries include Burmese of other colors, such as red, tortie and cream.

One other gene that's kind of fun -- the white-spotting gene, S. Capital S is spots, small s is no spots. Burmese don't have the white spotting gene, but the breeds that do occasionally see coats of twins. Technically, to be twins as felines, they must share a placenta. This requires that they be the same gender and the white spotting gene will be exhibited as a mirror reflection pattern.

I hope that this helps to explain the genetic make-up of the colors of the Burmese. It's rather a lot of explaining, but the essences of it all is Chart 6. Up to there, I'm showing what that chart means. After that, it is specific examples. The four colors of Burmese are controlled by the two gene pairs shown in Chart 13. The rest is showing how I got there, what color those cats would be, and defining terms and table styles.

Note: since this article was written the U.S. registries have been gaining recognition for the colors introduced by adding the sex-linked orange gene. For more information, see The Orange Gene: Sex-Linked Genetics over Dessert.

(published with permission by Darbie Marlin)

Read more about it:
Basic Genetics - Coat Colors with Red
Burmese Mating Color Charts