Post by Haley on Jan 12, 2010 15:21:10 GMT -6
Genetics
Genetics are difficult, it took me a while to figure it out, but I'm glad I finally got it. They are so fun to do, ha. Genetics are passed down to foals (punette squares can help), and like this site said, "I find that the easiest way to think about horse color is to imagine it as a series of building blocks. Each color is built from a group of genes that act differently when combined with different bases."
All the information below is from this site.
All horse colors are built on only two base colors, black (E) and chestnut (e). Black is dominant to chestnut, and chestnut is thus recessive. That means that a horse carrying 2 black genes (EE) will be (homozygous) black; a horse carrying one black gene and one chestnut gene (Ee) will also be black (but heterozygous); and a horse carrying two chestnut genes (ee) will be chestnut (always homozygous). So if two heterozygous black horses are bred together (Ee +Ee), they have 1 chance in 4 of producing a homozygous black (EE), 2 chances in 4 of producing a heterozygous black (Ee), and 1 chance in 4 of producing a chestnut. Two chestnuts bred together (ee + ee) can only produce chestnut.
There are many different shades of chestnut such as: liver chestnut, golden chestnut, dark golden chestnut, red chestnut, black chestnut, flaxen chestnut, flaxen black chestnut, and flaxen liver chestnut.
Red chestnut
Liver chestnut
Black chestnut
There are also different shades of black. Not all black horses do fade in the sun, and when they do, they can resemble bays and or liver chestnuts.
Non fading black
Faded black
Many horse colors are the result of dilution genes acting on the base colors. They all work similarly in that they dilute the main body color, but not always the color of the legs, mane, and tail. Bay is the most basic dilution color, and it is caused by the agouti gene diluting black. The black body hairs are diluted to a shade of brown while the legs, mane, and tail remain black. Like most dilution genes, agouti is dominant, so if a horse carries it, it will be expressed.
Agouti is not actually a separate gene, but rather a piece of the black gene called an allele. It can occur in three forms: A-agouti (meaning the horse is bay), a-non agouti (meaning the horse remains black), and At-brown (a color often confused with dark bay, but genetically different from bay).
Shades of bay: light bay, dark bay, blood bay, wild bay (the black on his legs is restricted to just his joints and pasterns)
Light bay
Dark bay
Wild bay
Brown (At) is also a dilution that acts on black as mentioned above. Though it looks similar to dark bay, it is genetically different. Brown horses are characterized by having a black coat with brown hairs on their muzzles, flanks, inner forearms, and inner thighs. Seattle Slew is an excellent example of this color.
Cream: Unlike agouti, which can only act on the black gene, cream can modify any color it acts in conjunction with, though it is most commonly seen combined with chestnut, bay, and black. The cream gene is an incomplete dominant, meaning it is always expressed when it's present, but it acts differently in its heterozygous (1 copy of the gene) and homozygous (2 copies of the gene) states. Simply put, horses with one copy of the cream gene will have a diluted coat; horses with 2 copies will have a doubly diluted coat. Double dilutes always have blue eyes. The cream gene does not effect black hairs in it's single form (nCr), only in it's double form (CrCr).
Palomino: Chestnut + 1 Cream gene
Chestnuts have no black hairs, so the entire coat is diluted. The mane and tail are almost always white. There are several different shades of palomino like the isabella palomino.
Cremello: Chestnut + 2 Cream genes
Cremello is basically a very pale palomino color---white markings are still discernable against the pale cream colored coat. Cremellos have blue eyes and light colored skin. (The only true pink skin is under white markings.)
Buckskin: Bay + 1 Cream gene
Because the cream gene doesn't affect black hairs, the dark points remain even after the bay body color has been diluted. There are several different shades of buckskin such as the buttermilk buckskin.
Perlino: Bay + 2 Cream genes
When two cream genes are present, the body color becomes very pale, and the black points are diluted to a red or brown color.
Smoky Black: Black + 1 Cream gene
The cream gene has very little affect on black hairs in its single state, so smoky black is very hard to distinguish from brown or (very sooty) dark bays. Often the best way to tell if the horse carries the cream gene is to have it genetically tested.
Smoky Cream: Black + 2 Cream genes
This Akhal Teke is thought to be a smoky cream. Notice how his points are still a darker shade than the rest of the body.
Dun: Like the cream gene, the dun gene is also a dilution gene, but it is a complete dominant rather than an incomplete one, meaning heterozygous (Dd) and homozygous (DD) duns look the same. It is often considered a "primitive" color because most very ancient breeds are predominantly or entirely dun, i.e. Przewalskis, Tarpans, etc. Duns are characterized by certain markings known as dun factors. They usually consist of a distinct dorsal (or eel) stripe down the back, leg barring (or zebra stripes), and cobwebbing on the face. As with the cream gene, the dun gene only dilutes the body color, not the points. The dun can affect all colors. For example, you could have a blue roan dun, sable ivory champagne dun, or a dunalino (palomino dun).
Red Dun: Chestnut + Dun
The chestnut color is diluted to a sandy color, but the mane, tail, and points remain chestnut. The dun factors tend to be the same reddish brown color as the points.
Bay Dun: Bay + Dun
The body color is diluted to a sandy color, but the points remain dark. This mustang shows another typical characteristic of duns---the light colored hairs on top of the mane and at the dock of the tail.
Black Dun: Black + Dun
This color is also called grulla, slate dun, or mouse dun. Once again, the points remain dark while the body color is lightened.
Dunalino: Chestnut + Cream + Dun
This is a palomino dun. The points are dark and the body is lightened.
Dunskin: Bay + Cream + Dun
This is a dunskin, a buckskin and dun put together. Buckskins and duns are very different from each other.
Silver Dapple: Silver dapple (also called taffy) is a dilution gene that only affects black pigment, but not red (chestnut) pigment. It acts by changing black pigment to a chocolaty color, and thus bays to a reddish, sometimes dappled color. (This dappling is unrelated to that caused by the grey gene.) While the legs are often only slightly affected by the silver dapple gene, the mane and tail change to a pale, flaxen color. Because of this, flaxen chestnuts are easily confused with silver dapple horses (and vice versa). This color is found primarily in Rocky Mountain Horses, other related gaited horses, Mustangs, and Shetland Ponies. Heterozygous is (nZ) and homozygous is (ZZ).
This is silver dapple on black. Note the diluted mane and tail. Some silver dapple blacks fade with sun exposure to a dappled chocolate or even greyish-brown shade. The latter is very common in Shetland Ponies.
This is Smooth As Silk, a Rocky Mountain horse owned by Fair Chance Stables exhibiting the dappled chocolate shade of silver black.
This is April Sunshine, a light silver dapple bay Rocky Mountain Horse owned by Overlook Stables.
This is Amaretto Blu, a darker silver dapple bay Morab. The manes and tails of silver dapple horses often darken as they age, but they generally do retain flaxen tips.
This is a silver dapple buckskin: black + agouti + cream + silver dapple.
This stunner is the aptly name Chocolate Roan, a roan silver dapple black RMH owned by Volz's Mountain Horses.
This is Classic's Shogun, a roan silver dapple bay RMH. He is also owned by Volz's Mountain Horses.
Champagne: The champagne gene is a simple dominant dilution gene, much like dun. In other words, if a horse carries the champagne gene, he will be champagne in color. Champagne combined with chestnut is called "gold," with bay is "amber," with brown is "sable," and with black is "classic." Sometimes, champagne is combined with the cream gene as well, producing a color known as "ivory." It is known to act in conjunction with other dilution genes (i.e. dun), but those colors have yet to be named. Champagne horses are usually born with bright pink skin that becomes freckled as they age. They are also born with blue eyes that change to a hazel shade as they get older. The champagne gene is found most often in Tennessee Walking Horses, Missouri Foxtrotters, American Saddlebreds, and Quarter Horses. Heterozygous is (nCh) and homozygous is (ChCh).
Gold Champagne: Chestnut + Champagne
The chestnut color is diluted to a golden color, similar to palomino. There is a distinguisihable difference because champagnes have hazel eyes and freckled skin. Many champagnes have a metallic or pearly sheen to their coats. (This is Glenknoll's Moregold, an ASB stallion.)
Gold Ivory Champagne: Chestnut + Champagne + Cream
The chestnut color is diluted by the champagne and cream genes to a pale cream color, similar to cremello. There is a distinguisihable difference because champagnes have hazel eyes and freckled skin. Many champagnes have a metallic or pearly sheen to their coats. (This is Chance's Favorite Ivory, a TWH stallion.)
Amber Champagne: Bay + Champagne
The bay color is diluted to a golden color, similar to buckskin, but again is distinguishable because of the hazel eyes and freckled skin. (This is Doc’s Golden Champagne, an APHA gelding
co-owned by Natalia Tate and Jordan Pierce.)
Amber Ivory Champagne: Bay + Champagne + Cream
The bay color, affected by both the champagne and cream genes, is diluted to a pale cream color similar to perlino, but again is distinguishable because of the hazel eyes and freckled skin. (This is Wind D's Champ Dominator, a TWH stallion ownder by Rockin' B Walkers.)
Sable Champagne: Brown + Champagne
The brown color is diluted to a mousie grey-brown shade with darker points, very similar to classic champagne. (This is California Champagne, a Paint Stallion owned by Carolyn Shephard.)
Sable Ivory Champagne: Brown + Champagne + Cream
The brown color is diluted to a pale golden-brown shade with darker points, very similar to silver bucksin. It is of course distinguishable by the hazel eyes and freckled skin. (This is Kya, a QH owned by Tara Novotnoy.)
Classic Champagne: Black + Champagne
The black color is diluted to a mousie grey-brown shade with darker points. Just like the gold and amber champagnes, classic horses have the telltale hazel eyes and freckled skin. (This is Go Boy’s Champagne Pride, a TWH stallion owned by Laura Kidder.)
Classic Ivory Champagne: Black + Champagne + Cream
The black color is diluted to a pale silvery grey-brown shade with slightly darker points. Just like the gold and amber champagnes, classic horses have the telltale hazel eyes and freckled skin. (This is Topaz Merry Go, a TWH stallion owned by Bill Howes.)
Double Cream Ivory Champagne: Any Base Color + Champagne + Cream + Cream
Champgane combined with cremello, perlino, or smoky cream creates an irridescent, nearly white coat. These horses have very pale skin and very faint freckling.
