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Bengal Genetics

The Genetics of the Bengal

You can quickly learn the basics of the genetics that affect the coat of the Bengal cat.

However, before we get going, let me add one proviso. The research into cat genetics is continuing all of the time, and even in the last couple of years new genes have been identified. So if I am behind the times, or if you know more or better than I do, I would love to hear from you so that I can update this page.

This page mostly concentrates on coat type, colour and pattern. It does not cover all of the genes affecting the coat, but concentrates on those affecting the Bengal.

How Genes Work

The first thing to understand is that all genes come in pairs.

When an egg is formed it only contains one half of the pair of the dam’s genes - the other half of the pair goes into a different egg. Similarly, when sperm is formed, each only contains one half of the pair of the sire’s genes.

When the sperm fertilises the egg the two halfs join together to form a pair of genes again - so the kitten (other than in exceptional circumstances) always inherits half it’s genes from it’s dam and half from it’s sire.

It is not true that the sire’s genes are ‘stronger’ than the dam’s genes. After all, the sire inherited half his genes from his dam, and the dam inherited half her genes from her sire - so how can they be? Both the dam and sire should take equal credit for a ‘good’ kitten, and equal credit for a ‘bad’ kitten. It all depends on how the genes mix and match.

There are different genes that affect the pattern of the coat (spotted or marbled), and the colour of the coat (brown, snow, blue, silver, chocolate, cinnamon), and the type of coat (long or short haired). Each gene has a specific job to do.

Dominant and Recessive

Some genes are dominant and some are recessive.

The pair of genes could be made up of two dominant genes, or two recessive genes, or one of each. Where a cat has one dominant and one recessive gene as a pair, then the effect of the dominant gene will always affect the cat. The recessive gene will (usually) be invisible.

For example the short hair gene is dominant, and the long hair gene is recessive. So if the pair of genes in a cat is made up from one short hair gene (dominant) and one long hair gene (recessive) the cat will be short haired.

However, there are exceptions to this rule as some genes seem to be more ‘strongly’ dominant than others. This is usually described as being ‘incompletely dominant’.

The ‘Buzz Words’ - Homozygous and Heterozygous

Two very long words that have a simple meaning.

If a cat has a pair of genes of the same type then they are ‘Homozygous’. So a long haired cat, that has a pair of long haired genes is ‘Homozygous for long hair’, and a short haired cat that has a pair of short hair genes is ‘Homozygous for short hair’.

If the cat has a pair of genes that are not the same, then they are ‘Heterozygous’.

For example, a short haired cat could have one short hair gene and one long hair gene - this cat is Heterozygous.

Charting the Genes

A simple way to work out what kittens your cat might have, is to build a simple chart, and work out the combinations of genes.

I’ll continue to use the short and long hair genes, as they are the simplest example to start with.

Start by drawing a chart that is 3 boxes wide and 3 boxes deep. Ignore the top left hand box. Now fill in the the top row with the stud’s genes, and in the left hand column the queen’s genes.

In the example below, both the stud (at the top) and the queen (at the side) have one short hair gene and one long hair gene. The symbol for the short haired gene is ‘L’ and the symbol for the long haired gene is ‘l’.

Notice that the dominant and recessive genes use the same letter, but the dominant gene is in upper case (L) and the recessive gene is in lower case (l).

Now take the symbol from the left hand male box (L), and combine it with the top one from the female (L).

Now add the symbol from the left band male box with the bottom one from the female.

Now do the same for the right hand two boxes:

You should end up with:

Top left, you have L L - two short haired genes (L) - this kitten will be short haired (homozygous)

Top right, and bottom left - you have one L and one l - one short haired gene and one long haired gene - these two kittens are short haired but carry long hair (the short hair gene is dominant, so the long hair gene is ‘invisible’)

Bottom right is l l - two long haired genes - so this kitten is long haired.

So the average that you would get from this mating are half the kittens being short haired, but carrying long hair (heterozygous), 25% being Long Haired (homozygous) and 25% Short Haired (homozygous).

Remember though, that these are only averages. Some eggs may die before they are fertilised, some sperm may never get that far, and then fertilised eggs may not survive. And you never know which ones will actually go full term.

So don’t expect to always get one long haired kitten in every litter of four. You have to repeat several matings before the ‘averages’ start to show up.

You can use this chart to work out the coat type, pattern or colour of any of the genes below - though the chart gets rather big and complicated if you try to chart more than one gene at a time - as you have to allow for every combination that might occur.

To work out the combinations of one gene, there are four possible combinations (the male carries a pair, and the female carries a pair). But to work out the combinations of two genes together (e.g. marbled or spotted, and snow or brown), there are sixteen possible combinations. As you might guess, the boxes get a bit big and complicated, and it is easy to lose track if you try to do too many combinations at a time.

Just as an example, here is a box where both the male and the female are brown spotted, but where they both carry marble and snow. Marble is recessive to spotting, and snow is recessive to brown.

So out of the mating of two brown spotteds who both carry marble and snow you would get (on average for 16 cats):

3 snow spotted, 2 of which carry marble
9 brown spotted - 2 carrying snow, 4 carrying snow and marble, 1 carrying marble and one homozygous
1 snow marble
3 brown marbles, 2 of which carry snow

Bengal Genes

These are the main genes that affect the Bengal, with an explanation of each of them. As said previously, research is still taking place and new genes are being discovered all the time, so if you know more, please let me know (contact details at the bottom of the page).

I have included some genes that do not relate directly to the Bengal, as they help clarify how other cats differ.

Birth Defects