This is ERRP's official rarity chart.
Rare trait passageRare traits with no clear passage pass at 10% if one parent has the trait and 25% if both parents have the same rare trait.
Traits with clear passage: pearl, mushroom
Traits without clear passage: lacing, brindle, somatic, chimeric, vitiligo
Traits with both:
-Mismarked appaloosa: Must roll appaloosa, then roll according to the no-clear-passage rates listed above.
-Chubari/tetrach: Must roll grey, then roll according to the no-clear-passage rates listed above.
-Bloodmarks: Must roll grey, then roll according to the no-clear-passage rates listed above.
-Bider marks: Must roll homozygous dominant for BOTH dun and sooty (StySty DD), then roll according to the no-clear-passage rates listed above.
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Note: the underscore (_) listed denotes that both a recessive or dominant letter can be subbed in. For example, To_ means that both ToTo and Toto can be listed without changing the phenotype.BlacksE_ / aa
Occur with at least one dominant copy of extension (E in the genotype) and no dominant copies of agouti.
JetSun-fadedChestnutsee / __
Occur when there are no dominant copies of extension. Agouti can be dominant or recessive; either way, the presence of agouti alleles or lack thereof does not change the presentation. (Agouti dominance: A+ > A > At)
StandardLiverHoneyDark Liver BayE_ / A_
Occur when there is both a dominant copy of extension and (standard, A) agouti; both alleles can be either homozygous dominant or heterozygous.
StandardBloodDarkSeal BrownE_ / At_
Occurs when there is a dominant copy of extension and seal agouti (At). There cannot be a dominant copy of regular or wild agouti, as those are dominant over seal agouti.
Wild BayE_ / A+_
Occurs when there is a dominant copy of extension and wild type agouti (A+).
Tobiano To_
A white pattern. Tobiano is characterized by four white legs, but almost always also presents with at least a colored face flank. The white in tobiano typically crosses the spine line. Heterozygous tobiano typically is more classic presentation; homozygous tobiano causes more extreme variations whether this is minimal or maximum white. When dominant, it can cause cat tracks, which is a messy colored spotting pattern in the white. Note that while belton spots often occur in tobianos, they can also occur in horses that simply have white leg or facial markings. Tobiano does not cause blue eyes.
TobianoCat tracksBelton SpotsOveroOo
A white pattern that is only allowed in the heterozygous form, as the homozygous form causes Lethal White Overo Syndrome. White in overo does not cross the spine line. Overo typically causes unusual white markings on the face and can cause blue eyes.
SplashSpl_
A white pattern that presents as smooth-edged white on the coat starting from legs upward. The spine line is almost never crossed by the white. Splash commonly occurs in a minimal form with white, such as a bald face, being present on the face and legs in some fashion. Blue eyes frequently occur with splash. Heterozygous forms tend to be more minimal, whereas homozygous forms tend to be more extreme.
SabinoSb_
A white pattern that causes irregular white markings of varying size. Sabino is typically characterized by the presence of a large facial blaze and four white legs. Sabino can cause an irregular roaning pattern on the coat even without the presence of roan (Rn_). It may also cause blue eyes. Heterozygous forms tend to be more minimal (such as the characteristic white four legs and blaze, maybe a white stomach patch), whereas homozygous forms tend to be more extreme (with more white on the body).
SabinoRoaning from SabinoAppaloosasLp_
There are various presentations of appaloosa. The leopard complex (Lp) causes mottled skin, stripes hooves, and/or progressive varnish roaning of the coat and is required to show the effects of a patterning gene; however:
ERRP does not use PATN1. It is not necessary to use it in the genotype; instead, appaloosa passes as similar to the parents' presentation of appaloosa. Ordinarily, the patterning gene PATN1 as well as many other unidentified ones affect the amount of white appaloosa patterning. In ERRP, the leopard complex is the only gene associated with appaloosas and is capable of producing blanket/leopard and snowcap/fewspot appaloosa patterns without a pattern gene.
Informative reads on Appaloosas:
one -
twoVarnish AppaloosaLp_
A gradual roaning of the coat found in appaloosas. This can be far more extensive than true roan (Rn) in that it can affect the legs and face. Can be paired with other types of appaloosa.
Varnish Blanket AppaloosaBlanket AppaloosaLplp
Snowflake AppaloosaLpLp, Lplp
Can be paired with other types of appaloosa.
Leopard AppaloosaLplp
Snowcap AppaloosaLpLp
Fewspot AppaloosaLpLp
PintaloosaAny combination of a white marking (tobiano, overo, sabino, splash) with appaloosa. (Pictured is tobiano + blanket appaloosa).
Mismarked AppaloosaThis is a faulty area of the horse's coat that simply displays the base color without appaloosa affects. It is similar in concept to blood marks in greys and genetically similar to somatic mutations.
DunD_
Primitive markings including striping on the legs, a dorsal stripe, a face mask/darkened face, sometimes stripes on the shoulders, and sometimes cobwebbing on the face. Dun on black creates Grullo.
Dorsal stripeLeg barringShoulder stripingGrulloSilverZ_
A dilute that lightens the mane and slightly dilutes black to dark brown-chocolate on horses with a dominant copy of extension. On black horses, it can cause extreme dappling. The extent of dilution does not change depending on zygosity.
CreamCr_
A dilute that lightens the color of the coat; the extent of the lightening depends on zygosity. Homozygous forms cause blue eyes.
Heterozygous cream on black creates
Smoky BlackHomozygous cream on black creates
Smoky CreamHeterozygous cream on bay creates
BuckskinHomozygous cream on bay creates
PerlinoHeterozygous cream on chestnut creates
PalominoHomozygous cream on chestnut creates
CremelloChampagneCh_
A dilute that creates a shiny lightening of the base color. The skin is often a purplish-pink with freckles. The eyes are typically hazel. Reverse dapples (wherein the dapples are darker than the coat, rather than lighter) occur commonly with champagne. The extent of dilution does not change depending on zygosity.
Champagne on a black horse creates
Classic ChampagneChampagne on a bay horse creates
Amber ChampagneChampagne on chestnut creates
Gold ChampagneChampagne on seal brown creates
Sable ChampagnePearlprlprl
A recessive dilute that is located on the same locus as cream. It only affects the coat when it is homozygous recessive or codominant with Cream. Pearl carriers can be written in a variety of ways, such as: crprl, Prlprl, nprl
Black PearlBay PearlChestnut PearlCream Pearl (Crprl)Mushroommshmsh or mumu; Mshmsh or Mumu (carrier only)
A recessive dilute that only affects chestnut-based horses (aka recessive for extension ee). It causes the ordinarily chestnut coat to take on a greige coloring and lightens the mane and tail of the horse. Note that while these often look similar to silver dapples (blacks), mushrooms rarely have dapples.
Flaxenff, Ff (carrier only)
A recessive gene that lightens the mane and tail in chestnut-based horses (aka recessive for extension ee).
SootySty_
Sooty is a gene that causes black hairs to intermingle in the horse's coat, causing the appearance of dark shading over the body. It can cause the manifestation of dapples, countershading, and sometimes mimic dun patterning. The inheritance pattern is unknown, but considered to be relatively dominant.
Sooty on BaySooty on ChestnutRoanRn_
A gene that causes white hairs to be distributed throughout the body, leaving the points (face, legs, mane and tail) untouched. Corn marks occur when the horse gets an injury; as the hair grows back, it often grows back the color of the coat with no white effect. Note that while appaloosa, sabino, and rabicano cause a roaning effect, they are not actually caused by roan.
Blue/Black RoanBay RoanRed RoanCorn marksPangare+ Pangare
Pangare is a modifier that causes a lightening of the coat of the undersides and muzzle. It is not able to express on black horses (E_ aa). The inheritance is currently unknown, so artists may add it to the genotype as shown above and pass it according to a 50/50 chance. In the past, pangare in ERRP was represented with PngPng or Pngpng; this may be replaced with + Pangare in offsprings' genotypes.
RabicanoRb_
A gene that causes a roaning effect concentrated on the barrel of the horse.
Bider MarksThis is an extremely rare marking that only occurs in horses homozygous dominant for both sooty and dun (StySty DD).
GreyG_
This is a gene that causes the hair on the coat to gradually lighten out to a white-gray color as the horse ages. The skin and hooves of the horse are unaffected and are left the color of the horse before the greying occurred. Zygosity does not change the speed of greying; greys usually grey in similar fashions to their lineage, so a fleabitten will often have fleabitten offspring.
Dapple Grey (on a Black base)
Steel Grey (on a Black base)
Rose/Mulberry Grey (on a Bay or Chestnut base)
Fleabitten Grey:
Black -
Chestnut.
Blood Marks: These are essentially a faulty area of the coat that remain the original color.
Chubari/
Tetrach Marks: These are rare circular marks with sharp borders that occur on Grey horses. As the horse greys, they eventually become invisible.
Gulastra PlumeThis is a white tail that presents in the absence of white markings near the tail region (white tails caused by white patterning near the tail are just considered apart of the paint). The cause is uncertain; some believe it is tied to sabino, others believe it is tied to minimal paint patterns. In ERRP, gulastra plume may present with any white patterns (tobiano, sabino, overo, splash).
Grease SpotsThese are markings that appear as spots that are several shades darker than the horse's coat; they resemble grease spots on clothing. The cause of them is unknown, and as such, they are not listed in the genotype.
Birdcatcher SpotsThese are small, white spots that pop up on (typically solid) horses' coats randomly throughout their life. They are believed to pass genetically and can be listed in the genotype as +BC Spots, but this is not mandatory.
Reverse DapplesThis is an uncommon pattern of dappling in which, instead of the inside of dapples being lighter than the outside, the inside of the dapples are lighter than the outside. As with regular dapples, they are mainly seasonal, and there is no 'official' gene that causes dapples. However, sooty and champagne can be a common contributor.
LacingThis is a rare pattern that causes a white cob-web type pattern on or around the back of affected horses. The pattern usually grows in size as the horse ages. There is believed to be some level of genetic inheritance involved with lacing. Note that lacing and reverse dapples can appear similar; the difference is that reverse dapples have a wide, cloudy border, whereas lacing is thinner and has a sharper border. Also, reverse dapples do not necessarily occur on the back.
Brindle and Reverse BrindleBrindle is an extremely rare coat phenomenon usually caused by chimerism. It appears as a dark striping pattern. Reverse Brindle is similar, but rather than a dark striping pattern, it causes a white striping pattern. It is generally not passable in real horses, but is passed in the species according to ERRP's rare roll rates.
VitiligoVitiligo is caused by a condition that leads to depigmentation in patches. The area may regain pigment or it may remain depigmented for the remainder of the horse's life. There is not a known heritage pattern, but is passed in the species according to ERRP's rare roll rates.
Additional ExampleSomaticSomatic mutations cause patches (usually only one patch) of a horse's coat to express a different color than the horse's base coat (but one still logically possible for the horse given its parents). It is caused by a mutation in the cells of that area of the coat, causing certain genes to be turned 'off'. This results in, for example, bays with black somatic patches, palomino with chestnut somatic patches, etc. It is not passable in real horses, but is passed in the species according to ERRP's rare roll rates.
ChimerismChimerism occurs when two (fraternal) twins merge in the womb, causing a horse to carry two copies of genetic material. The coat will have two different coats both in the phenotype and in the genotype. Note that blood marks are often mistaken for chimerism. It is not passable in real horses, but is passed in the species according to ERRP's rare roll rates.
Example:
Dam: Black blanket appaloosa; EE aa Lplp
Sire: Bay tobiano; Ee Aa ToTo
Potential Offspring: Bay tobiano x Black blanket pintaloosa; Ee Aa Toto x Ee aa Lplp Toto--
Manchado, dominant white, sunshine, etc--all genes not found on the rarity chart--are not found in ERRP. ---
Note that ERRP does not locate KIT genes on the same locus, so tobiano, sabino, and roan may exist simultaneously in both heterozygous and homozygous forms.
