Bengal Cat Genetics
I
want to start with a usefull link on cat genetics.
Dr.
Leslie Lyons - UC Davis (Feline Genetics Home Page)
Traditionally the various coat color and effects
are described in alphabetical order by Locus (location) but I find this
order more helpful as it builds from the skin up.
B Locus: Primary Color
Black
= B - Dominant - if a cat receives this gene from one of it's parents,
the cat's primary color is black.
Chocolate = b - Recessive to B
Cinnamon = bl - Recessive to B, b
Most Bengals have black as their primary color. The colors
Chocolate and Cinnamon are recessive colors that exist in the breed.
A cat can carry Chocolate or Cinnamon and not exhibit the color so
it is important to know a breeding cats genetics. If two cats are
bred that carry for Chocolate, there is a chance of the kittens being
Chocolate. If two cats are bred that carry for Cinnamon, there is
a chance of the kittens being Cinnamon. Chocolate and Cinnamon are
not recognized colors in some registration organizations and cannot
be shown there. For a cat to be chocolate or cinnamon he or she must
receive the gene from both parents. For the colors Blue, Lilac and
Fawn please see the D Locus.Chocolate, b, is recessive to black. Chocolate
is not recognized in most registries of the Bengal cat. Cinnamon,
bl, is recessive to both black and chocolate. The pawpads and the
tail tips are Chocolate and Cinnamon. This is one of the main ways
to identify that a cat is not a brown/black tabby.
C
Locus: Color Exhibition (The Full Color Locus)
C
= Full Color - Dominant
cs = Colorpoint Siamese (the gene that causes Seal Lynx Point) - Recessive
to C
cb = Colorpoint Burmese (the gene that causes Seal Sepia) - Recessive
to C, incompletely dominant to cs
ca = Blue eyed Albino - Recessive to C, cs, and cb
c = Pink eyed Albino - Recessive to C, cs, and cb
cl = Leucistic Albino - Recessive, details to come
You will note that there is no gene listed for Seal Mink.
Seal Mink is caused by the combination of cs and cb genes. A Seal
Mink receives Seal Lynx Point from one parent and Seal Sepia from
the other. Just like other recessives a cat can carry the genes and
not display them. Bengals carrying for "snow" are quite common and
surprise white kittens can show up from two brown marbled or brown
spotted cats. Both cs and cb are an albino variant found in the Siamese
and Burmese breeds. True albino come in two forms, blue eyed and pink
eyed. An albino Bengal will not display a pattern even if it has the
Agouti gene. Albino cats often have a number of health related issues
including vision problems, skin problems, and sensitivity to light.
Another form of albinism is called leucistic, this is the condition
that causes white tigers and lions with naturally colored eyes. A
number of animal species produce occasional leucistic individuals.
A Locus: Agouti Banding
Agouti = A - Dominant - Pattern Displays
Non Agouti = a - Recessive - Pattern Does Not Display
This is the gene that determines if the tabby pattern
will display or not. All Spotted or Marbled Bengals are Agouti/A -
the pattern displays. However an all black Bengal, a Melanistic, is
Non Agouti - the pattern does not display and the primary color, Black,
is seen everywhere. Non-agouti is recessive and a cat must receive
the gene from both parents for the pattern to be prevented from displaying.
The gene can hide for several generations in a line.
E Locus: The Extension Gene (sometimes called the
amber gene)
Extension = E - Dominant -Full Extension
Non Extension = e - Recessive - Non-extension
The
Extension gene (red factor) has two alternative states (alleles).
The dominant allele E produces black pigment (Eumelanin) in the coat.
The recessive allele e produces red pigment (Phaeomelanin). A cat
with ee will be highly rofused, even what some breeders call Sorrel
by not extending the black of the Agouti Banding to the end of the
hair shaft. Little research has been done on the extension gene in
cats but large amounts of infromation on the gene are available for
cows, dogs, horses, and rabbits. The gene appears to work in tandem
with the Agouti gene producing someof the brilliant colrs seen in
the bengal breed.\
Wide Band Locus: Agouti Banding
Variable
Wide
Band = Wb - Dominant
Not Wide Band = wb - Recessive
Wb means that the agouti banding is made wider, thus
more uniform and not as "ticked" looking. It is not known if this
is a gene perse or a group of polygenes at this time. The wide band
polygene affects the Agouti portions of the shaft where the emelanin
(black) is turned off making them wider, sometimes so wide that the
additional affects of the Agouti banding are pushed off the shaft
giving the shaft a single color. It may be the source of the "clear
coats" we see in the Bengal Breed.
Mc
Locus: Pattern Flow
Mackerel
Tabby = Mc - Vertical Flow
Classic Tabby = mc - Circular Flow
A Mackerel Tabby pattern means the flow of the cats pattern
is more vertical, up and down. This is where the vertical barring
can come from. The Classic Tabby pattern means the flow of the pattern
is circular on the body of the cat. Many Bengals have the pattern
flowing in a circular manner on their sides. But where does the Horizontal
Flow we see in the Asian Leopard Cat and many champion bengals come
from. There are two theories:1.) The gene combination Mcmc creates
Horizontal Flow. The problem with that theory is you don't see Horizontal
Flow in any other breeds that don't use some form of leopard cat for
their foundation2.) A new theory is that there is another gene being
labeled mz that comes from the Asian Leopard Cat, and it is found
on the same Locus. If this theory is true it may be the gene that
makes the Horizontal Flow we strive for, and mzmz may be what makes
some of the cutting edge cats so great.
Sp
Locus: Pattern Interruption
Interrupted
Pattern = Sp - Dominant - The pattern is interrupted producing "spots"
Uninterupted Pattern = sp - Recessive - The pattern is continuous creating
a "marbled" effect
This is where our spots and marbles come from. Little
is know about the genetics that make the differences in the spots
at this time. Clearly there is a genetic piece causing round spots,
arrowhead spots, two color rosettes, two color arrowhead rosettes
and paw print rosettes. It is hoped that this genetic database will
help us get to the point where we can develop provable theories behind
the genetics.
T
Locus: Ticking Locus
Ticked
= T - Dominant - Agouti Band covers all but the base of the shaft
Not Ticked = Ta - Recessive - Agouti band pushed off the shaft of the
hair
Ticking contributes to the intensity and contrast of
the pattern by determining how much of the shaft is the base color
(Black, Chocolate or Cinnamon). A highly Ticked cat will only have
a narrow Agouti yellow band at the base of the shaft in the pattern.
While T is dominant not receiving the gene from both parents does
reduce the intensity indicating that the dominance may be incomplete.
A cat that is TaTa will not show the Agouti pattern because the primary
color is pushed off the shaft (like an Abyssinian).
I
Locus: Inhibitor (also called the Silver gene)
Color
Inhibited = I - Dominant (incompletely dominant to i)
Color Not Inhibited = i - Recessive
This gene affects the display of the yellow pigment on
the Agouti banding by suppressing it. Working in tandem with the Agouti
gene suppressing the production of phaeomelanin pigment (yellow/red),
it has little or no effect on the emelanin pigment (black) production.
With no production of phaeomelanin the shaft is left only with whatever
emelanin production is occuring. If there isn't any, the shaft is
white, if there are trace amounts the shaft is gray. The end result
is that the shaft of the hair will look gray or white while tipped
with the primary color (preferably black). This gene is dominant and
only one parent needs to carry the gene for it to express. This is
a very difficult gene to work with however and the color inhibition
may be incomplete. In some cases break though of the phaeomelanin
(yellow/red) occurs (Robinson's 142). This seems to only happen in
silver cats that have one Inhibitor gene from one parent, and a Non-inhibitor
gene from the other parent. This suggests that perhaps while the Inhibitor
gene is dominat it may be incompletely dominant, or that there is
a limit to the amount of phaeomelanin (yellow/red) it can supress
when not homozygous.The resul is that by allowing the yellow to brown
pigment to display the cat has what is called tarnish. Tarnish is
very undesireable.
D
Locus: Color Density
Dense
Color = D - Dominant
Diluted Color = d - Recessive
This gene affects how the color cells in the shaft of
the hair are dispersed. Normally the color cells are evenly distributed
along the shaft of the hair, this is Dense Color and it is what we
see in most Bengals. However if the color cells in the shaft of hair
clump together they don't demonstrate the full coloring of the primary
color making the shaft look "frosted" properly called Dilute. To be
dilute the cat must receive the recessive d from both parents as dd
... DD and Dd will not show the diluted or frosted appearance. This
is where the Bengal colors Blue, Lilac and Fawn come from. Blue is
actually diluted Black, Lilac is actually diluted Chocolate, and Fawn
is actually diluted Cinnamon.
O
Locus: Orange
O
= Orange - Dominant
o = Not Orange
- Recessive
Orange is the elimination of all eumelanistic (Black)
pigment by converting the proteins into phaeomelanin (yellow). It
comes from the Torbie influence used as an early outcross in the Bengal
breed. This is not to be confused with rufousing. It is sex linked
carried on the X chromosome. Females may exhibit the full Torbie or
Calico, males will be all orange except in rare instances of non-disjucntion
of the zygote. The Orange gene is not common but it has surfaced in
the breed from time to time.
Mi
Locus: Mica Glitter
Non-glittered
= Mi - Dominant
Glittered = mi - Recessive
This gene is still partially theory. It affects just
the tips of the hair shaft. In the recessive form, mi, when we look
at the hair shaft under a powerful microscope we see what appear
to be small flecks of Mica, a very reflective mineral, embedded
in the tip of the hair shaft. We hope to post pictures of this effect
on this page in the future. This gene did not come from the Asian
Leopard Cat but rather from a domestic cat used by Jean Mill in
her early breeding program. Another form of glitter runs the full
length of the shaft, please see the Sa Locus for more information
on that glitter type.
Sa Locus: Satin Glitter
Sa = Non-Satin - Dominant
sa = Satin - Recessive
This gene is still very much in the theory phase. This
gene is seen in several species. Inter-species genetic comparison
is common. Many mammals are genetically similar and traits found
in one species may also crop up in another.
The satin gene is well documented in some rodent species
including mice and rabbits. It is also believed to be in Bengals
coming from some of the domestic cats that were used as outcrosses
in the Bengal such as Siamese, Burmese, Ocicat and Egyptian Mau.
This gene creates little bubbles of air in a sheath that surrounds
the full length of the follicle. These air bubbles catch and refract
the light giving the coat a glittered effect which, while similar
in some respects to the Mica Glitter, it is also very different.
This gene also makes the shaft of the hair very smooth and gives
the cats coat a very soft and silky feel. The more satin shafts
in the coat the silkier and softer the fur.
L
Locus: Hair Length
L
= Short Hair- Dominant
l = Long Hair- Recessive
The long hair gene doesn't crop up very often in the
Bengal breed, but it is out there. Bengals are intended to be short
hair but the occasional long hair kitten crops up. They are gorgeous
and loving and make a great friend. They are not currently showable
and are usually only available as beautiful pets. A small group
of breeders in Europe have decided to work with the long hair gene
under the new breed name Cashmeres.
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