As a kid I remember being confused by the logic of dog genetics presented in cartoons. When two dogs had puppies, the boys looked like the dad and the girls looked like the mom. I can only guess that this lack of originality was an attempt to cash in on the new character's resemblance to an older character that had already won people over, but where's the fun in that? Being the animal nerd that I am, I wanted a realistic guide to prevent such blandness.How to use
Much of this has not yet been proven in studies with real dogs, so if you want to learn more about a real dog it is useful to research the specific breed or likely breeds that are in the dog's background.
Each locus is a spot which can hold two possible alleles out of any number present in the whole species. All together the alleles (genotype) give the final appearance (phenotype). To decide the appearance of offspring, give each parent a full list of genes to describe their appearance and "breed" them by randomly selecting alleles (if they are not homozygous for the same allele). I like to use www.random.org/
and have dominant alleles represented by odd numbers and recessive alleles represented by even numbers. Alleles are listed from most dominant to least dominant.
indicates alleles I have made up to determine shade of color (the cause of which is still largely a mystery), or different patterns to produce more variety (most of these are thought to be controlled by modifiers on a completely different locus).
indicates theoretical genes I am using in this way until I can find a reference that shows that a trait has been identified and inheritance pattern described.fav.me/d69s69z
shows shades of color I have assigned.Terminology
Eumelanin- Black pigment in skin, hair, and eyes. All eumelanin will be affected by chocolate or dilution genes. Genes that only affect eumelanin in hair include progressive graying, seal, recessive red (by preventing its production), and merle.
Phaeomelanin- A red pigment produced only in the hairs. It is affected by dilution but not chocolate. Genes that affect phaeomelanin include brindle, the agouti gene on the K locus (by allowing its expression in hair along with eumelanin), the intensity locus, and urajiro.
Locus- A place in the DNA which hold alleles, genes encoding traits. There is no limit to how many alleles can be present in a species, but each individual can only carry two per locus.
Phenotype- The measurable effect of a gene. Genes with complete or incomplete dominance affect the phenotype, while recessive genes need two copies to be expressed.
Full dominance- Only one copy is needed to display a trait; recessive alleles will not be expressed.
Recessive- Any gene on a locus that is blocked by a dominant gene.
Homozygous- When both alleles on a locus are the same.
Heterozygous- When a locus carries two different alleles.
Incomplete dominance- A dominant gene that does not completely mask a recessive one, creating a blended phenotype. Examples include merle and white spotting.
Co-dominant- Two genes that are fully expressed when heterozygous.
Epistatic- A gene on one locus which masks the expression of genes on another locus. Example- recessive red to the K locus.
Polygenic inheritance- The phenotype shows a gradient based on the interaction of two or more gene pairs. This can be represented with a + for increasing a trait, a 0 for keeping a trait stable, and a – for decreasing a trait. Example- the extreme variance of weight between breeds.Size and Shape
Photo References: fav.me/da6v0fySize Locus:
Determined by IGF1 (insulin-like growth factor-1), and possibly a series of other genes which act as modifiers. Full explanation leonca.deviantart.com/art/Dog-…
Type of dominance- Incomplete.
I (medium to large).IB (intermediate size).
B (small).Mutations which change limb and skull length are inherited separately. A dog with a normal skull is mesocephalic. A dog with a shortened jaw is brachycephalic. A dog with an elongated skull is dolichocephalic.Limb Length Locus:
Micromelic achondroplasia produces shortened limbs but leaves other body proportions alone. Example- Dachshund. Type of dominance- Incomplete.
Mn (normal limbs).MnMs (slightly shortened limbs).
Ms (shortened limbs).?Polydactyl Locus:
Dewclaws on hind paws. Example- Great Pyrenees. Type of dominance- Complete.
Pn (normal hind paws).
Pp (dewclaws on hind paws).Upper Jaw Length Locus:
Maxillary achondroplasia shortens the upper jaw. Example- Boxer. Type of dominance- Incomplete.
Un (normal upper jaw).UnUs (slightly shortened upper jaw).
Us (shortened upper jaw).Lower Jaw Length Locus:
Mandibular achondroplasia shortens the lower jaw. Example- Pug (also has maxillary achondroplasia). Type of dominance- Incomplete.
Ln (normal lower jaw).LnLs (slightly shortened lower jaw).
Ls (shortened lower jaw).?Dolichocephalic Locus:
The skull is elongated, with upper and lower jaws staying in proportion. May also cause limb bones to be longer and more slender. Example- Borzoi. Type of dominance- Incomplete.
Dn (normal skull).DnDe (slightly elongated skull).
De (elongated skull).When combined with dwarfism this may create legs which are shortened but more fine-boned and less likely to be crooked.?Clinorhynchy Locus:
The palate turns downward from the base of the skull, giving a flat face with no “stop.” Most evident in bull terriers, but also seen in some long-skulled breeds such as borzoi. Tandem repeats in a gene allow exaggeration within a closed gene pool over many generations. Represented here in a simplified form. Type of dominance- Incomplete.
Cn (normal skull).CnCl (moderately downturned skull).
Cl (downturned skull).?Stocky Locus:
Lean build with extra powerful muscles. Type of dominance- incomplete.
SB (stocky build).SBSb (moderately stocky).
Sb (normal build).Skin?Wrinkled Skin Locus:
Type of dominance- Polygenic, two pairs of alleles with plus modifiers.
++/++= Extremely wrinkled skin.
++/+0= Very wrinkled skin.
++/00 and +0/00= Moderately wrinkled skin.
00/00= Normal skin.Ears
?Ear Shape Locus
: Type of dominance- Incomplete.
*O (semi-pricked ears).
*Od (dropped ears). Incompletely dominant to Or and o.
*Or (rose ears). Incompletely dominant to o.
*o (pricked ears).?Ear Size Locus:
Type of dominance- Polygenic, two pairs of alleles with plus and minus modifiers.
+ and – cancel each other out, and 0 holds size steady. Example: -0/-+ give a final number of -1, a little smaller than average.Tail Shape
?Tail Shape Locus
: Type of dominance- some complete, some incomplete.
*V (bobbed tail) Two copies are lethal. Full dominance to all others. May be erect or straight depending on second gene carried.
*Vq(corkscrew tail. May shorten and kink other types if carried together.
*Vs (sickle tail, true breeding).VsVt- Saber tail, blended phenotype.
*Vt (straight tail).VtVc- Saber tail, blended phenotype.
*Va- (saber tail, true breeding).VaVc- Sickle tail, blended phenotype.
*Vc (curled tail).Eye Color
Photo References: fav.me/d67pd8k
*EB (blue eyes). Eyes are blue regardless of other pigmentation or pattern. There are probably at least two loci with alleles that cause this phenotype, which is mostly seen in Australian Shepherds and Siberian Huskies. Type of dominance- Complete.
*E (normal brown or amber eyes).
*e- (heterochromia). Odd eyes unrelated to white spotting or merle. Example- Siberian Huskies.
?Eye Shade Locus
: Determines darkness of eyes. Type of dominance- Polygenic, two pairs of alleles with plus and minus modifiers.
2, 3= Dark medium.
1, 0, -1= Medium.
-2, -3= Light medium.
Example: ++/0-= 1/medium shade.Tongue Color?Black Tongue Locus:
Deposits eumelanin in the tongue in Chow-Chows and Shar-Peis. Other breeds and mixes with black on their tongue may be descended from these breeds, have a different gene that does the same thing, or have a non-heritable birthmark. Type of dominance- complete.
BT (black tongue).BTBt (black or spotted tongue).
Bt (pink tongue).Coat Type
Photo References: fav.me/da6v0fy
?Hair Length Locus
: Base length. Type of dominance- Complete.
*LS (smooth coat).
*LM (medium coat).
*l (long coat).
?Hair Length Modifier Locus
: Variation within base length. Type of dominance- Polygenic, two pairs of alleles with plus modifiers.
++/+0, ++/00, and +0/00= Average.
00/00= Shortest.?Feathering Locus:
Hair is longer on ears, elbows, back of hind legs, and tail. Example- Saluki. Type of dominance- Incomplete.
*FE (heavy feathering).FEfe (moderate feathering).
*fe (smooth).Non-shedding Locus
: Hair grows continuously. Example- poodles and many terrier breeds. Type of dominance- Complete.
N (normal hair growth).
n (non-shedding).Wire-haired Locus
: The coat has a rougher, bristly texture and may have more facial hair, including a beard. Type of dominance- Complete.
w (non wire-haired).Curly-haired Locus
: Example- Curly Coated Retriever, Irish Water Spaniel. Type of dominance- Complete.
CU (straight hairs).
Cu (curly hairs).nn CuCu- coat will form cords if allowed.Hairlessness Locus
: Type of dominance- Incomplete (except in American Hairless Terrier). HH is lethal.
h (has hair).Coat Colors and PatternsK Locus
: Type of dominance- Complete (K), Co-dominant (kb
). Photo References: fav.me/d5syu1q
K (dominant black). Blocks expression of red hairs unless the dog is ee at the E locus. Default eye color- brown. Default nose color- black.
(brindle). Black stripes on areas with red hairs. Full body brindle is seen when the dog expresses ay
at the A locus.
(allow expression of agouti). Allows patterns of black hairs over a base of red hairs.
?Brindle Modifier Locus
: Type of dominance- Polygenic, two pairs of alleles with plus modifiers.
00/00= light (red brindle)
+0/00= medium light
++/+0= medium dark
++/++= dark (black brindle)B Locus
: Modifies black hair and skin pigment to chocolate, aka brown/liver/red. Type of dominance- Complete. Photo References: fav.me/d5tenou
B (normal black).
b (chocolate). Eyes- amber. Nose- chocolate. Red hairs- unaffected. Three b alleles exist, but the cause of different shades of chocolate is unknown. Nose may be a lighter pinkish shade when also expressing recessive red.D Locus
: Dilutes black hair and skin pigment to blue, aka charcoal/slate gray.
D (normal black).
d (blue). Eyes- amber to darker brown. Nose- same as fur color to darker blue. Red hairs- intensity is slightly desaturated.bb dd- Dilutes chocolate to Isabella, aka diluted brown/lilac. Eyes- may be paler amber. Nose- similar to hair color. Red hairs- intensity is slightly desaturated.
?Eumelanin Intensity Locus
: Determines darkness of chocolate, blue, and Isabella. Type of dominance- Polygenic, two pairs of alleles with plus modifiers.
+0/00= medium light
++/+0= medium dark
++/++= darkG Locus
: Progressive graying, aka steel blue/silver/faded brown. Puppies are born with normal black/chocolate/blue/Isabella pigment and lighten with age. Black masks, if present, are not affected. Mostly seen in breeds with long or non-shedding coats. Type of dominance- Complete.
G (progressive graying). Eyes- not affected. Nose- not affected. Red hairs- not affected.
g (no progressive graying).
: Brown undertone without expressing bb. Back has darker hairs. Only seen in solid black or blue short-haired coats.
SE (normal black).
Se (seal).E Locus
: Decides if the dog is able to produce eumelanin in hairs. Type of dominance- Complete. Photo References: fav.me/d5tn4rr
(mask). Pattern of eumelanin in facial hairs. Affected by all genes which alter eumelanin except for progressive graying.
(grizzle in Salukis, Domino in Afghan Hounds). Rare allele which modifies tan points when at
is expressed on the A locus.
E (allows black hairs, no mask).
(K epistatic sable/Cocker Spaniel sable). Pattern similar to heavy shaded sable or grizzle/domino. Two copies overrides dominant black. Lightens with age. Lightens intensity of eumelanin if agouti is expressed- dirty red.
e (recessive red). Aka clear red. No black hairs expressed. Eyes- unaffected. Nose- black or Dudley (lightening of mid nose, may be seen in lighter red dogs or any red dog as it ages). Epistatic to the K locus.
?Mask Modifier Locus
: Determines extension of mask. Type of dominance- Polygenic, two pairs of alleles with plus modifiers.
00/00 and +0/00 = Small mask- tip of muzzle only to most of muzzle with eye spots and ear borders.
++/00 and ++/+0 = Medium mask- muzzle/eye spots/cheek spots/ears, eye spots may connect with muzzle.
++/++ = Chest shading- most of face, throat, chest, and possible sooty markings on legs and sides. Creates Phaeomelanin Pooling if white spotting is expressed- legs/chest show darker red than the rest of the body, as if the pigment is pooling and intensifying on the areas bordered by white.
: Intensity of phaeomelanin in hairs. Type of dominance- Polygenic, three pairs of alleles with plus and minus modifiers. Photo References: fav.me/d5tqk3r
++/++/++= Darkest (red)
00/00/00= Average (fawn)
--/--/--= Palest (silver)
+ and – cancel each other out, and 0 holds shade steady. Add and final shade is a result of a positive, neutral, or negative number.
5= Dark gold.
3, 4= Gold.
1, 2= Light gold.
-1, -2= Light fawn.
-3= Pale fawn.
-5= Pale cream.
Example: 0+/0-/+0= 1, light gold.
: Pattern of red hairs on face and undersides lightened to white. Black hairs are not affected. Most well known in the Japanese Akita and Shiba Inu.
*U (no urajiro).
*u (urajiro).M Locus
: Merle. Affects eumelanin in hairs, producing patches of solid color mixed with areas that have white hairs blended in. Eyes- may be normal or blue. Nose- may have pink spots (depigmentation). Red hairs- unaffected, though some clear sables appear to show patches of red or black in the merle pattern (yellow merles). Black with merle= blue merle, chocolate with merle= red merle, blue with merle= slate merle, Isabella with merle= lilac merle. Type of dominance- Incomplete. Photo References: fav.me/d5uerwg
m (no merle).MM genotype- double merle. Extreme limitation of pigment during development. Amount of color is based on white spotting pattern, ranging from piebald appearance to pure white. Hearing problems and ocular deformities are possible.
?Merle Intensity Locus
: Type of dominance- Polygenic, two pairs of alleles with plus modifiers.
++/++= Heavy merle, most black areas lightened.
++/+0= Heavy medium merle.
++/00= Medium merle.
+0/00= Light medium merle.
00/00= Light merle, few black areas lightened.
?Merle Base Color Locus
: Type of dominance- Polygenic, two pairs of alleles with plus modifiers.
++/++ and ++/+0= Pale color in lightened areas.
++/00= Medium color in light areas.
+0/00 and 00/00= Dark color in lightened areas. Blue merles may have a muddy brownish look.
: Causes patches of different shades of lighter color in merles. Type of dominance- Complete.
*Tw (normal merle).Harlequin Locus
: Lighter areas in merle are lightened to white or white with gray patches. If a pattern on the A locus is expressed, the dog will have black patches over white where normal merle would have been, and red patches over white where normal red would have been. HAHA is lethal. Type of dominance- Incomplete.
Ha (normal merle).
?Merle Infiltration Locus:
Allows merle pattern to appear in clear sables and recessive reds- yellow merle. There is also a kind of “black and red” merle, where merle markings are not restricted to the head and back as in typical sable merles. Perhaps the same gene interacts with “heavier blacked” sables or other agouti locus genes to create a black on red pattern which extends across the whole body. Type of dominance: Complete.
*MI (normal merle).
*Mi (merle infiltration).A Locus
: Pattern of black hairs over a red base. Expression requires that the dog have no K at the K locus and is not ee at the E locus. Type of dominance- Complete. Photo References: fav.me/d5vghli
(sable). Pattern of black hairs on head and back. 6- Smoked sable (black shading over larger portion of the body than other sable types). Example- some American Akitas.
4, 5- Shaded sable (distribution of black hairs on back and head with widow's peak pattern).
3- Tipped sable (noticeable sprinkling of black hairs on the back and head).
2, 1, 0, -1, -2, -3, -4, -5, -6- Clear sable (few to no black hairs on the back, but may have black whiskers).
(agouti). Aka wild type, grizzle, wolf gray, badger, sesame. Pattern of hairs on back and head that are banded with black and red, like on a wolf.6- Heavy/black agouti.
-2, 1-, 0, 1, 2, 3, 4, 5- Normal agouti.
-3, -4- Husky patterned/extended white agouti.
-5, -6- Minimal black agouti.
(tan points). Pattern of solid black over red.6- Minimal tan points. It may be hard to find any red, especially if mask is present.
0, 1, 2, 3, 4, 5- Traditional tan points.
-1- Creeping tan. Ratio of black to red is close to 50/50. Often undesirable in purebreds. May be a modifier on a different locus, but for simplicity sake I’m sticking it here.
-5, -4, -3, -2- Normal saddle. Females may have bitch stripe (lightened area running down the back).
-6- Light saddle. May follow normal or reduced pattern, and has a grayed look instead of solid black.
a (recessive black). Identical phenotype to dominant black. Rare, mostly seen in herding breeds.ee aa could result in solid white coat.
?Agouti Modifier Locus
: Determines amount of black extension. Polygenic, three pairs of alleles with plus and minus modifiers.
++/++/++= Heaviest black extension.
00/00/00= Intermediate black extension
--/--/--= Least black extension
?White Spotting Locus
: Patterns of melanocytes which produce no pigment, starting at extremities and moving towards the head and back. White spotting shows over all patterns of black and red. Paw pads are depigmented to pink and claws are depigmented to light yellowish color. The true number of alleles or loci is unknown. Type of dominance- Incomplete. Photo References: fav.me/d5xbc3u
(Panda markings in German Shepherd Dogs). Dominant, markings resemble irregular Irish spotting. Two copies are lethal before birth. Not part of the White Spotting Locus but placed here for simplicity.
S (solid color).Ssi with 00/00, +0/00, ++/00 and Ssp with 00/00- Solid.
Ssi with ++/+0, and Ssp with +0/00, ++/00, ++/+00- White trim.
Ssi and Ssp with ++/++- Pseudo-Irish.
Ssw- Flashy white.
(true breeding or white collar Irish). Large white blaze on the muzzle extending between the eyes, thick white collar on neck extending to chest, often more white on front legs than back, white tail tip. Example- Boston Terrier.sisp, sw- Irregular Irish or piebald, depending on modifiers.
(true breeding piebald). When combined with S the piebald gene may have no effect or show limited white depending on modifiers.spsw- Irregular low color piebald.
(extreme piebald). Color is restricted to small patches on top of head/around eyes/ears. During development, reduced white on the head increases the chance of deafness and blue eyes.White Spotting Extension Locus
: Determines spread of white spotting. Type of dominance- Polygenic, two pairs of alleles with plus modifiers.
++/++= Maximum white spotting for base pattern.
+0/00, ++/00, and ++/+0= Regular white spotting for base pattern.
00/00= Minimal white spotting for base pattern.
?Split Face Locus
: Modifier of white spotting that causes half of the face in Irish or Piebald patterns to be white. Type of dominance- Complete. Photo References: fav.me/d639n40
*F (normal white spotting).
*f (split face).
: A large spot of color appearing on the head or neck in a dog with white markings covering the area. Possibly hereditable. Type of dominance- Complete.
*LO (no lozenge).
*Lo (lozenge).Roan Locus
: Modifier of white spotting. Sprinkling of colored hairs in white areas. Type of dominance- Complete.
r (no roan).Ticking Locus
: Modifier of white. Small spots of color in white areas. Dalmatian spotting is a modifier on a different locus, but for simplicity sake I’ve stuck it in the T Locus. Type of dominance- Complete.
T (regular ticking).
td (Dalmatian spots. One copy- regular ticking. Two copies- Dalmatian spots).
t (no ticking).
?Ticking Modifier Locus
: Polygenic, two pairs of alleles with plus modifiers. TT and Tt may create different phenotypes, but since the expression is so varied I’ve gone with plus modifiers.
++/++= Heavy ticking (large spots over whole body, but most concentrated on face and legs).
++/+0= Medium heavy ticking.
++/00= Medium ticking.
+0/00= Light medium ticking.
00/00= Light ticking (small spots on face and legs).White spots on chest/toes
: Developmental incomplete migration of melanocytes. Can appear over any pattern and is not heritable. Photo References: fav.me/d5xbc3u
- (not present).
: The C locus and P gene are possible causes of albinism in dogs. Type of dominance- Complete. Photo References: fav.me/d5tqk3r
*C (normal coloring).
Causes very faded markings instead of blocking the ability to produce pigment. Skin is pink and eyes are blue. Type of dominance- Complete.
*LE (normal coloring).