xX Dingo Creek Horse Genetics Xx

[Bella.]

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A Guide to Genes

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For Guest Artists: Guest Artists must have a basic knowledge of genetics, but it is still acceptable to require some help.
For Artists: Artists must have at least a basic knowledge of genetics, but it is still acceptable to require minimal assistance.
For Breeding Artists: Breeding Artists must have a firm knowledge of genetics and genetic inheritance, little assistance is acceptable.

Terminology
• Alleles - Each gene is made up of two letters. Each one of these letters is referred to as an allele.
• Gene: a trait that is possessed/shown.
• Genotype: The genetic write up of the genes the horse shows or carries.
• Phenotype: What you can physically see in the horse. A horse may be a carrier for a gene, however it will not show in it's phenotype because it is not seen.
• Carrier: A gene that may be passed on to offspring, however the trait is not visibly seen in the parent horse.
• Homozygous - displaying two of the same alleles. Eg. AA or aa.
• Heterozygous - displaying two different alleles. Eg Aa
• Dominant - An allele that masks another allele of a given trait. Is represented as a capitol letter.
• Recessive - An allele that is only visible when homozygous. Represented by lowercase letters.

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[Bella.]

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Base Genes
• E - Controls black pigment. Is represented as completely black in both heterozygous and homozygous expressions. If a horse has no E gene (represented as ee) then the horse can only be chestnut.
• A - Dependent on the E gene as it restricts where black pigment occurs and causes a bay colouring. Mane and tail are black or dark brown. If a horse has no E gene it may still carry the A gene, however it will not show. There are three variations of this trait. At only removes black from the soft spots (belly, muzzle, inner legs, eye). A restricts black to just the ears and legs while the rest is bay. A+ restricts bay to just the lower legs.
• W - Dominant White is the most dominant gene and will override all other genes. This is a very rare gene and is often confused with just extensive white markings. A horse cannot have two white genes as the foals die within their first few days. This gene restricts pigment completely, meaning horses are white from birth.

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[Bella.]

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Dilution Genes
• Cr - Cream colouring, causes lightening of the horses coat. Heterozygous (Crcr) will lighten the coat slightly whereas homozygous dominant (CrCr) will lighten the coat even more. It affects each base colour differently causing smoky or cream variations.
• D - The dun gene lightens the coat and reveals primitive markings. These include barring of the legs, dorsal stripe, face mask lighter coloured hairs in the base of the tail and edges of mane among others. This gene affects each colour differently causing a wide range of dun colours.
• prl - The pearl gene is only visible when it is homozygous recessive, or combines with the Cream gene. It dilutes the coat to a lighter, warmer colour. It affects each colour differently. Pearl and Cream are linked together, so if a horse has two pearl genes it may not have the cream gene. If a horse has two cream genes, it cannot show the pearl gene. A horse may have one of both the peral and the cream gene.
• Ch - The champagne gene causes lightening of the coat and pink skin underneath. It is considered a rare dilution and affects each colour differently. It is expressed the same in its heterozygous and dominant homozygous form.
• F - The flaxen gene only affects chestnut horses, and must be expressed and homozygous recessive in order to be shown. A horse that is not chestnut may carry the flaxen gene however it will not be visible.
• Z - The silver dilution gene in it's heterozygous form is expressed as nZ rather than Zz. It affects the coat the same way in it's heterozygous form and it's dominant homozygous form. Mostly the tail and mane are affected, however some lightening of the coat may occur. It will only affect horses that have an E gene.

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[Bella.]

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Modifier Genes
• G - Contrary to popular belief, grey is not actually a horse coat colour. A horse can look grey however this is due to the presence of the grey gene, causing a loss of pigment through age. Grey affects each base colour differently, with black going through stages such as dapple grey, steel grey, medium grey, dark grey, fleabitten and white, while chestnut and bay horses can also appear rose grey and mulberry grey.
• STY - The sooty gene mixes black hairs into the horse coat, predominantly on the back, neck and hips. It displays the same in it's heterozygous and dominant homozygous form.

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[Bella.]

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Marking Genes
• Rb - The rabicano gene mixes white hairs into the horses coat mostly on the belly, but may extend to between the front legs and the underside of the tail. It displays the same in it's heterozygous and dominant homozygous form.
• Rn - The roan gene mixes white hairs into the coat of the horse, primarily all over the body excluding the head and legs. Both homozygous roan and heterozygous roan appear the same, however if a horse is homozygous for roan it may not show any trace of sabino, dominant white or tobiano.
• Sb - Heterozygous Sabino is the formation of solid white markings on the belly of the horse, which may have a roan appearance on the border of the markings. In it's homozygous form, a sabino horse can be up to 100% white, and is often confused with Dominant White. If a horse is homozygous for sabino, it may not have the genes for roan, dominant white or tobiano.
• To - The tobiano gene causes rounded patches of colour that appear on a white background. Their heads are usually coloured while their legs from the knees down will be white. In tobiano horses, white always crosses the topline of the horse causing white in the mane and tail. These white patches can be as little as a small white patch on the withers (known as Minimal Tobiano) to a full-body white horse with very few coloured patches. This gene displays the same in it's heterozygous and homozygous form, however if homozygous for tobiano a horse cannot have the genes for roan, sabino or dominant white.
• O - Overo is essentially the opposite of tobiano - markings form rough jagged patches along the horses body, the face will often be white while the legs from the knees down will be coloured. White will not cross the topline. A foal will die within the first few days of birth if it is homozygous for overo.
• Spl - The splash gene shows differently in its heterozygous and homozygous state. In it's heterozygous form, it is very difficult to identify as they often only have markings on their lower legs and muzzle, looking like regular socks and a snip. In it's homozygous form, the white forms a pattern similar to what you would imagine if a horse was dunked in white paint. The bottom-side of the horse (belly, back of the legs, neck) as well as the face are covered in white.

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[Bella.]

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(oops! on the image I mean SNOWCAP, not Blanket!)

The Appaloosa Gene
• I won't go into detail about the gene, as it is called 'Leopard Complex' for a reason! The Appaloosa gene is denoted by LP, and this gene is not yet fully understood. So this is how it goes:
lplp - not written as all horses with a specific gene are recessive homozygous for it. Appaloosa markings do not show.
Lplp - Can be either Varnish Roan (light covering), Leopard Appaloosa, Blanket Appaloosa.
LpLp - Can be either Varnish Roan (dense covering), Fewspot Appaloosa, Snowcap Appaloosa.
The last appaloosa pattern, the Snowflake Appaloosa, can occur with heterozygous or homozygous dominant genes.

A horse can have the roan gene as well as the Leopard Complex gene. In the case of a Blanket Appaloosa, the spots are extended through the roan and not restricted to the blanket.

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[Bella.]

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Other Genes
The following markings are not fully understood or controlled by genes in reality, however Dingo Creek has created some extra's to fit with inheritance behaviours of the species.
• Birdcatcher Spots (Bi) - All Dingo Creek horses possess this trait. It is extremely rare for one to be born/created without any at all. It is a recessive trait, and a horse will need to be homozygous recessive for the trait in order for it not to show. All Dingo Creek horses are homozygous dominant for the trait unless otherwise specified in the genotype.
• Lacing (La) - This gene is recessive and a horse must be homozygous recessive in order for it to show. White markings appear like netting over the horses back, may be expressed in a minimal form or extend up the neck and down to the tail in it's maximum form.
• Grease Spots/Bend Or Spots (Gr) - Dominant gene causing darker spots or patches on the horses coat, may be seen as a subtle colour variation to almost black. Is expressed the same in it's heterozygous and homozygous dominant state.
• Brindle (Br) - A recessive gene causing 'patchy stripes' of darker or lighter shades along the horses coat. The markings can be minimal and only seen in a few patches or as extensive as brindle covering most of the horses coat excluding the legs and head.
• Gulastra Plume (Gp) - Similar to the silver gene, however this gene causes only a lightened tail while the main and coat hair remains undiluted. Can range from a fully white tail to a dark silver in the end half of the tail. This is a recessive gene and must be homozygous in order to be seen.
• Pangaré (Pn) - Only visible in the absence of black pigment. Dominant gene, is expressed more heavily in it's homozygous form than it's heterozygous form. This gene causes the dilution of the soft spots (belly, flank, inner legs)
• Calico (Cr-) - The calico gene is an extension of the cream gene, and is only seen with a combination of the cream gene and the tobiano gene. A horse must have all dominant cream alleles affected by calico in order for the calico to show. Eg. a horse with two cream genes must have Cr-Cr- in order to show, while a horse with only one cream gene must have Cr-cr in order to show. A double cream gene horse may be a carrier for the calico colouring, denoted by CrCr-. Calico is basically patches that were missed by the cream gene. For example, Palomino is the result of cream on chestnut. A palomino calico tobiano would be palomino with patches of chestnut showing through.

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