Feline Genetics

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Basic Feline Genetics

Coat Colors: there are only two basic colors- Red/Orange (O) & Black (B) [variations are created by the density of the pigmentation or pattern expression which will be detailed further on]. White (W) is not a color but 'masks' or covers the true hair color. White can also occur only on specific parts of the body; known as Spotting (S).

Black (B) vs Non-black (b)
The shades of black & dominance is as follows:
Black (B-) > Chocolate/medium brown (bb/bb') > Cinnamon/light brown (b'b')

Red/Orange (O) vs Non-orange (o)

• (O) results in red hues and variations. The (O) allele replaces all other colors except white, the recessive (o) allows full expression of black and its variations.
• The non-orange allele is much more common in the overall population of cats. Orange is a sex-linked trait (meaning it is only carried by the X chromosome) thus most orange cats are male, since to be completely orange a female must inherit both (OO) alleles.
• For a female cat to be orange their father must be orange and their mother must carry at least one (O) gene (she must be ginger or the diluted form, or a tortie).
• Red color shows tabby markings- they might be ghost markings, which are barely discernible but still present- regardless of the presence of the non-agouti gene.
  
  • The intensity of the red/orange coat is due to an unidentified factor.

Tortoiseshell & Calico

• Females with (Oo) alleles show patches of orange due to the (O) allele, but also show non-orange areas (o), which create the distinctive coloring.
• Because orange is carried on the X chromosome, this coloring is almost exclusively female (XX), however in rare cases of males with chromosomal abnormalities (XXY) will exhibit the colors- because of the extra chromosome most of them are sterile.
• Approximately 1 in 3,000 calico/tortoiseshell cats are male
• Calicos are just tortie cats with the spotting gene.

White Spotting/ Piebald (S) vs No spots (s)

• (S) > (s); the cats that show spotting may show different white markings on their body, masking the true color where the spots occur.
• (Ss) (White shows on less than half the body) cats show white only in one or few areas of the body- most commonly on the feet, nose, chest, and belly- like tuxedo cats.
• (SS) (white shows on half or more than half of the body)- show big white patches/spots- like bicolors or harlequin cats.
• Completely white cats may be possible through the spotting allele and are differentiated from the white masking allele due to their eyes- which range from yellow, hazel to green.

Dominant White (W) vs Non-white (w)

• White masks/hides all underlying colors; it is not a true color
• White masking/dominant white cats are differentiated from a completely spotted white by their eye color- their eyes are blue or bright amber/orange.

Full Color (C)

• (C) expresses full color and dominant over the color points and albinos.
• (cb) also known as Burmese point shows a dark body with even darker points (extremities).
• (cb/cs) is known as Tonkinese points and is an in between color.
• (cs) also known as Siamese point shows a light body with darker points & intense blue eyes.
• (ca) albino w/blue eyes
• (c) albino w/pink eyes

Dominance is as follows:
C > cb > cs > ca > c

Density of color: is the pigment concentration in the hairs, and is what causes the different tones of orange or black.

Dense (D) vs Dilute (d)

• Diluted forms of black (and variations) and orange are recessive.
• When a cat has two of the recessive (dd) alleles, black fur becomes "blue" (appearing gray), chocolate fur becomes "lilac" (appearing light brown), cinnamon fur becomes fawn, and orange fur becomes cream.

Coat Patterns


Agouti/Tabby (A) vs Non-Agouti/Solid (a)

• The tabby pattern causes the hair to show bands of color that are lighter at the root but darker at the tip.
• Lack of the dominant agouti trait expresses a solid color (aa).
• Cats expressing an (O) orange color will show stripes regardless of the agouti gene.

Tabby Patterns:
Mackerel (Mc) vs Blotched/Classic/Marbled tabbies (mc)

• Mackerel is the basic wild type tabby gene; it produces thin stripes similar to fishbones and it is dominant to the Classic tabby (Mc) pattern which displays broad bands and spirals of dark color on a pale background.

• Brown mackerel tabbies are the most common in wild cat populations.

• Abyssinian ticked/non-patterned agouti tabby (Ta/ta)
• If the ticked marking (Ta) is present any other patterns are masked.
• They have virtually no stripes or bars, instead they have a sandy appearance.
• The residual ghost striping might be visible on on the lower legs, face and belly and sometimes at the tail tip, as well as a long dark line running along the back, usually in the spine.
• A (Ta/Ta) genotype will show virtually no ghost markings as compared to (Ta/ta).

Spotted (Sp) vs Non-spotted (sp) tabbies

• Spotting (Sp) is dominant to mackerel (Mc) and classic (mc) tabby patterns.
• Spotting is closely linked to mackerel (T) it breaks up the thin mackerel stripes to create spots.
• It may also occur on a classic tabby (tb) to produce jaguar-like rosettes.

Tabby pattern dominance is as follows:
Ta > (Sp >) Mc > (Sp >) mc

The agouti and tabby genes combine with the basic pigments to create the following patterns and colors:


Melanin Inhibitor Gene (I) vs Non-inhibitor (i)

• The inhibitor gene is dominant to the non inhibitor, and much like the agouti gene, it causes the hair root to be lighter- however unlike in a tabby which is a drab version of their base color- the hair is almost white.
• It is also known as the silver gene, although it just means the undercoat is white. (There are red silver tabbies).

Colorations resulting from the dominant inhibitor gene (I):

Silver tabbies

• Are genetically brown tabbies with the inhibitor gene.

Chinchilla/Shaded/Smoke

• Depending on the amount of color covering the silver/white at the hair root it is classified as:

1/8 of hair length colored at tip - chinchilla/tipped
1/4 of hair length colored at tip - shaded
1/2+ of hair length colored at tip - smoke

• Smoke has the particularity of being genetically solid, unlike tipped and shaded.
• There are also variations of smoke coloring; being darker or lighter smoke.

Coat length & texture:

Short (L) vs Long (l)
Short hair is dominant to long hair.

Normal (Hr) vs Hairless (hr)
Normal coat is dominant to hairless coat.

Normal (wh) vs Wirehair (Wh)
Normal coat is recessive to wirehair.

Normal (R) vs Rex coat/curly (r)
Normal straight coat is dominant to curly coat.

Ears & Tail:

Straight (cu) vs Curled (Cu)
Straight ears are recessive to curled ears.

Straight (fd) vs Folded (Fd)
Straight ears are recessive to folded ears.

Manx tail (M) vs normal (m)
The manx tail (stubby) is dominant to normal length tail.

Eye color:
Normal eye colors range from:


Blue eyes: are most common on white cats (most blue eyed white cats are deaf).
Can only occur on cats with any kind of white; be it dominant/masking, piebald/spotting or albinism.
Most colorpoint cats have blue eyes.
The only cats that can have blue eyes regardless of the presence of white is the breed Ojos Azules.
Ice blue: is a mutation and occurs very rarely.
Gray eyes: bluish-gray eyes are common in kittens, and will rarely remain so during adulthood. Gray is a variation of blue.
Greenish-yellow to gold: and all the ranges in between are the most common eye colors in cats.
Amber/orange/copper: have the most melanin and are considered the darkest colors a cat can have.

Notes: kittens are born with their eyes closed and start to slowly open them after one week of being born, and have completely opened them by the third week.
Kittens are born with blue-gray eyes, but change color as they age, reaching their permanent color at 3 months of age.


References:
www.eurocatfancy.de/en1/nav/cat-genetics/dominance_of_genes.html
www.fanciers.com/other-faqs/color-genetics.html#shading
ib.berkeley.edu/courses/ib162/Week3a.htm
www.catster.com/lifestyle/cat-genes-science-fur-color[/b]