Suwannee Cockers
The Place for Natural Merles and Sables
COAT COLOR AND MARKINGS GENETICS IN AMERICAN COCKERS--Page 2
THE ABC'S OF DOG GENETICS
So far about a dozen genes have been postulated to control the various colors and markings in all dogs, acting through chemical reactions in the blood, using hormones and proteins, and each of these dozen or so genes is thought to reside on a different chromosome, acting independently of each other. And the variations in colors in dogs are due to variations in the protein that forms the framework of the pigment granules.
It is thought that dogs evolved from a Southeast Asian small wolf species, over 100,000 years ago, and this species was surely a black animal, that was probably grizzled or had banded hairs, like most wolves today, and all of the various differences in coat color and markings in dogs today have been developed by people selecting various alleles of gene mutations that appeared naturally in the descendants of this small wolf species. And when we speak or write about these various alleles of genes in dogs, and other animals, the alleles of the genes are represented in genetic formulas by alphabet letters, with dominant alleles written in capital letters, and recessive alleles written in smaller letters.
The "A" Locus: The A Locus, or Agouti gene, controls the formation of the Agouti protein, becoming one of the mechanisms that controls the replacement of eumelanin (black/chocolate) with phaeomelanin (red/yellow) in the growing hair. The Agouti gene is named after a small Central American rodent of the genus Dasyprocta, with grizzled brownish or dark-grey fur, and this gene controls how the melanocytes are laid in both the hair shafts and on different parts of the body, and it functions in the colored areas of dogs, including the colored parts of parti Cockers.
Different alleles, or "flavors" of the Agouti gene are postulated in various breeds. In Shelties as many as 5 alleles may be active on the A locus, but most breeders of American Cockers thought that Cockers have only 3 alleles--traditionally called "A," for dominant black, "ay" for Sable, and "at" for tan points--with the "A" allele the most dominant, and the recessive alleles "ay" and "at" involved in the dilution of both Sable and Tan Pointed dogs. This scheme followed Little, but now geneticists believe that Dominant Black is located at the top of the newly formulated K Locus (for blacK). Thus Sable in Cockers is now on the top of the A Locus, with Tan Points more recessive, and there are now only three possibilites in Cockers on the A Locus, and the first is "Ay Ay", which is called Clear Sable, and is either a red or a blonde color, very similar to Buff in Cockers, depending on the dog's breed. Shaded Sable--"ay at" is next in dominance, and Tan Points "at at" completes the list of alleles on the A Locus for Cockers.
Dominant black: Dogs have a dominant form of black that completely obliterates all formation of phaeomelanin, or red/yellow pigment, and traditionally dominant black has been put at the top of the Agouti series on the A Locus. But "dominant black" is now thought by geneticists to reside on the K Locus, thus bringing the dominant black gene in dogs more in line with the operation of the Agouti locus in all other mammals that manifest dominant black, with the increasing dominance of the Agouti locus alleles resulting in increasing production of phaeomelanin (red/yellow) exclusively, and not black. The K Locus is epistatic, or hides, the A Locus, when dominant black is present, and thus dominant black on the K Locus acts just the same as Little's traditionally postulated "A" allele on the A Locus, which is why it has taken so long to figure out where dominant black resides.
Sable: Thus with the move of dominant black from the top of the A Locus--it used to be called "A"--Sable has now become the dominant gene on the A Locus and is called "Ay" and is usually referred to as the "Sable gene," in that it dilutes the solidly colored hair shafts to a paler color. In Little's scheme Sable "ay" was recessive, but it is dominant in the new K Locus scheme, so now it is referred to as "Ay" with a capital A.
When Sable is present, as in the black based Shaded Sable and white pup to the right, black usually dilutes to a red color, and brown dilutes to a tan color. But when other non-A Locus dilution genes--such as "d d" on the D Locus--are also present in the dog, various other shades of Sable--like blue, cream and silver--can also be produced. But we have read that under the new K Locus scheme, in order for a dog to be Sable, the alleles "E" for non-Buff, "k" for non-dominant black, "Ay" for Sable, and perhaps even "Em" for dark masks, must be present for the Sable (called Faun in some breeds) colors to appear, and this precise complexity of genetic alleles goes a long way toward explaining why Sable dogs are so rare in Cockers!
When the dog inherits two "Ay" genes--making it an "Ay Ay"--and the A Locus is not hidden by either Buff or Dominant Black--such a dog is called a "Clear Sable," and the dog's entire coat is diluted to a red or a golden yellow color--depending on other color modifiers--with no darker colored hair tips, or Shaded Sable overlay, and it is thought that some Buff colored dogs in American Cockers are really "Clear Sables" as the colors--Buff and Clear Sable--are almost identical looking. After observing two litters from our now retired silvery Buff girl named Darlin, pictured to the left, we believe that Darlin is a recessive Buff "e e" dog on the E Locus (discussed below) carrying two sable alleles--"Ay Ay"--as she threw so many Shaded Sable pups when bred to our Shaded Sable-Merle dog named Max, but never threw a Tan Pointed puppy. Darlin also threw several solid black pups, and a solid chocolate pup, making the "K k" designation very logical for her--making Darlin heterozygous Dominant Black. If so, then half of Darlin's puppies could express Sable--the ones that inherited the little "k"--and half couldn't express Sable--the ones that inherited the capital "K", and this coincides with the colors of her puppies. It is possible that Darlin could be "k k" on the K Locus and "Ay Ay" on the A Locus, making her a Clear Sable, but we don't think so because then ALL of her puppies would have been either Clear or Shaded sables. In Cockers the "Ay" allele is dominant to the Tan Pointed allele called "at."
So until we are more sure of Darlin's genetics, by seeing what her puppies and grandpuppies throw, we will stick with our original analysis of Darlin being a Buff dog, which is "e e" on the E Locus, discussed below, epistatic to "Ay Ay" Sable, as the E Locus is epistatic, or capable of hiding, the A Locus, and probably with "K k" on the K Locus. Interestingly, when tracing Darlin's pedigree we did discover two really rare Sable and white AKC champions back several generations--Ch. Samurai's Classic Gold CD, and his sire, the famous Ch Artistry's Soot and Cinders. These champion Sable dogs are very rare because Sables have not been allowed into the AKC conformation ring since 1997, but they can still be shown in both Canada and Europe.
Shaded Sable: As far as we know the new K Locus scheme does not change the Shaded Sable arrangement of alleles, as Sable has always been thought to be dominant over Tan Points. When a pup receives an "Ay" allele from one parent and an "at" allele from the other parent, it is called a "Shaded Sable" and is now designated "Ay at". In Cockers this is a dog that has its ground color diluted--black to red, and chocolate to tan--but in American Cockers an "overlay" of hairs of the original color remains, either black or chocolate, especially on the tips of the ears, sometimes on the muzzle as a "black mask," and along the back and sides of the dog's body. This Shaded Sable overlay may be very thick or rather sparse--it varies from dog to dog--but the Shaded Sable dog can usually be recognized by it "racoon eyes," or circles of lighter hairs around the eyes. Our mahogany red Shaded Sable-Cryptic Merle and white dog named Max, pictured here, also has black rings immediately around his eyes, which are sometimes also called "Egyptian Eyes." Max looks like a mahogany red Shaded Sable and white, but he throws half Merle puppies so Max is also a "hidden" or Cryptic Merle, and we discuss these dogs later in our section on Merles.
For a more thorough discussion of Sable dogs, you may go to our page that is devoted only to the Sable color, called About Sables, but if you go to that page now you will have to come back to this page through the "Articles" page.
Little next postulated an allele he called "aw" as the "wild wolf" color seen in the salt-and-pepper breeds. In these dogs tan is replaced with a pale cream to light gray and the hairs have several bands of light and dark color, with not just the black tips of a banded Shaded Sable. Keeshounds, Siberians and Norwegian Elkhound coats are thought to be due to the "aw" allele on the A Locus. "aw" is not seen in Cockers, and black and silvers in Cockers are thought to be caused by additional dilution genes, on top of Tan Points, such as the C Locus, or Chinchilla gene, or the D Locus, the Dilution gene.
Next in Little's theories comes "Saddle Tan," called "as" which is similar to the black and tan allele, except that eumelanin (black/chocolate) is restricted to the back and side regions, giving the marking the name "Saddle Tan." But this marking may also be due to another gene interacting with "at at" or Tan Pointed genotypes.
Tan points: The next recessive allele on the A Locus is called "at" and it is believed to be the allele that causes Tan Points on dogs, and is very commonly seen in Hounds, Dobermans and Rottwheilers. Tan Points in Cockers are highly variable, and tan areas can vary from mimimal Tan Points, with just a bit of tan on the eyebrows, to more tan on the muzzle, under the ears and under the tail with four tan feet, which is the most common Tan Points marking, and then to a dog with tan color all of the way up the legs and on the chest, which is usually called Terrier Tan. In Cockers Tan Points can express in black dogs--black and tans--and brown dogs--called chocolate and tans in Cockers--and in parti or "tri colored" dogs, that have various amounts of white areas--and Tan Points can be carried recessively in any colored dog. But Tan Points are not likely to be noticed in diluted Buff dogs, as the E Locus (Buff) series is epistatic to the A Locus, and the writer has never seen a red Cocker with Tan Points.
In Cockers it is believed that a dog can be either a Sable or have Tan Points, but not exhibit both types of dilution, as it is thought that although Tan Points are the result of the same dilution as Sable, Tan Points have another gene interaction that somehow restricts the Sable dilution to only the Tan Pointed areas, instead of all over the dog's body as in both Clear and Shaded Sables. And in some breeds Shaded Sables have banded hair shafts that are actually tipped in the darker color, like the original wild type of Agouti. One breed with Sable having dark tipped banded Shaded Sable hairs is Pomeranians, and Borzois have both types of Shaded Sable--dark tipped banded hairs and Shaded Sable dark haired overlays.
As mentioned above, geneticists now put dominant black on the K Locus, instead of the A Locus. And in Shelties and German Shepherds, at least, there is an allele called "recessive black" on the A Locus--called "a a"--which is more recessive than Sable and Tan Points, and the theory is that these recessive black dogs have Tan Points, but the Tan Points are completely hidden by black hairs. Little called recessive black dogs "a a" but we think that a recessive black dog would genetically be "at at" as it would throw all tan points. But we have not yet sorted out the relationships between the K Locus dominant black and the A Locus recessive black, and we will have to read a lot more about the K Locus before we can discuss this relationship. But the writer has had a black and tan puppy that was partly a recessive black, in that his Tan Points have black tips--called "Smoked Tan Points"--but when the dog is clipped the Tan Points look light again, with the darker tips clipped off.
There is also some speculation that Tan Points may be on an entirely different, but as yet unknown gene Locus, which would make the Tan Points' dilution different from Sable dilution. And it is also speculated that there may be another allele for the "Saddle Tan" or "Terrier tan" markings found in Terriers, but we have had a "Terrier Tan" Merle Cocker boy, so we are not so sure about this.
The "B" locus: This is the gene that makes the dog either black or brown (called chocolate in Cockers), and all dogs are either one or the other in their base color, and all other colors and markings are caused by modifiers of these two basic alleles of the B Locus. And brown is actually a dilution of black in the first place.
Black dogs: "B B" dogs are homozygous for black, and do not carry chocolate recessively.
"B b" dogs look black, but carry chocolate recessively, and can throw half chocolate puppies if bred to a chocolate dog, or one-quarter chocolate puppies if bred to another black dog also carrying the chocolate allele recessively. Two black dogs, with both carrying chocolate recessively, bred together would be written "B b" x "B b."
Chocolate dogs: All chocolate dogs are "b b," which is recessive, and they cannot carry black, and this allele affects eumelanin (black pigment) only, and does not affect red/yellow pigment. A chocolate dog "b b" bred to another chocolate dog "b b" will always produce all chocolate based puppies, with no black based pups possible. In some breeds "b b" is called red, as in Australian Shepherds. The chocolate color is caused by the "b b" granules of eumelanin pigment being smaller and rounder in shape within the hair shaft than the granules of pigment for black dogs, and thus reflecting light differently than the "B" black pigment, making the brown or chocolate hair shaft appear a lighter color--chocolate instead of black. The chocolate allele does not appear to affect Tan Points.
The C locus: This is called the Chinchilla gene, and it determines the depth of pigment within the hair, and we have read that the Chinchilla gene has a distinctly greater effect in reducing the red/yellow pigment than it does in reducing the black pigment. However, the recessive alleles of the C Locus do not express on Cockers that do not also express the Buff gene--"e e" on the "E" locus--again, a tiered arrangement of separate genes. However, all dogs carry the Chinchilla gene, expressed or not, and a solid black dog can carry the allele for even silver puppies recessively, and the C Locus may play a role in lightening eye color in dogs. Our chocolate tri Roan girl named Suzy Q has light hazel eyes, and she has a littermate that was a very light Buff and white, so it is possible that Suzy Q is carrying a very light Chinchilla dilution gene. However, chocolate is a dilution of black, and her light eyes may only be related to her diluted chocolate color, as no chocolate Cockers have fully dark eyes. We have read that the C Locus may play a part in the various colors of Sable dilution, but other writers attribute the different shades of Sable dilution--tan, cream and silver--to the D Locus.
There are thought to be three alleles on the C locus in Cockers--"C" "ch" and "xch"--which acting together cause the various shades of Buff, and the term "Buff" in American Cockers includes all of the E Locus expressed colors, from red to silver. The "C" allele, for full, non-diluted color, is dominant, and most dogs are "C C," which is called non-Chinchilla. Our Buff red girl named Sparkle is an example of a "C C" dog, as Sparkle is a Buff dog--"e e" on the E Locus, which is discussed later--that inherited two "C" alleles and is thus a deep red and not a Chinchilla diluted tan, cream or silver color. The "ch" Chinchilla allele, is next in dominance, and causes lighter shades of orange and Buff in Cockers, and the "xch," extreme Chinchilla allele, is the most recessive, creating silver shades of Buff. It does so by removing all or most of the phaeomelanin pigment, with only a slight effect on black pigment, if any at all.
However, Sparkle is not a fully Irish Setter red all over her body, so she obviously has some other sort of dilution going on, and she has thrown "Blue Sable" puppies, so perhaps she is also "D d" or "d d"on the D Locus dilution gene, discussed below, which will reduce red pigment to cream or silver, or she has some other sort of unknown dilution effect. Sparkle also has some white markings, but these may or may not be genetic, because although red dogs in many breeds are known to produce more white areas than other colors, due to still unknown color modifiers, it is also known that the muzzle, the chest and the feet are the last place on the puppy fetus to receive melanocytes, laying down pigment in the skin, and puppies in many breeds are born with these white markings, having nothing to do with color genetics, as the puppies were just born a day or two too early to get their full complement of pigment in these areas.
Also Sparkle's white markings are marked very much like Tan Points, and Sparkle does throw Tan Pointed pups, so her "Tan Points" may be white for some reason. Sparkle has thrown fully colored solid pups, even from a parti male, so we do not know if her white markings are genetic or not, but her white markings would definitely bar her from the Cocker show ring, thus also barring her wonderful personality traits from a show breeding program. But as we believe that a great Cocker can be any color or marking, and that temperament is more important than type or color, we had no problem breeding our beautiful Sparkle just because of a few white spots. The interactions of the various coat color and markings genes are just not fully known at this time, and we breeders are often left trying to "fill in the blanks" when it comes to understanding the interaction of these genes in our own dogs.
As stated above, we do not know if the C Locus dilutes the A Locus Sables also, which come in various diluted shades, including silver, cream, tan, red and blue, and we have read that A locus dilution is thought to be controlled by the D Locus--the so-called Maltese Blue dilution--so we will contain our discussion here to the interaction of the C Locus with the E Locus, which produces all of the various shades of Buffs. We do know that in diluted C Locus influenced hairs, the pigment is reduced by the formation of both fewer and smaller pigment granules, and phaeomelanin (red/yellow hair) is affected first, before eumalanin (black/chocolate hair), as well as phaeomelanin (red/yellow) hair being affected by the C Locus much more extensively than eumelanin (black/chocolate) hair, and we have read that some geneticists believe that the C Locus hardly affects black/chocolate hairs at all. And the reduced degree of black/chocolate pigment available in the first place in a "d d" diluted dog, as opposed to regular pigment in a "D D" or "D d" D Locus non-diluted dog, (the D Locus is discussed below) makes less pigment available in a dog that is double diluted on both the C Locus and the D Locus, and it may be that both the C Locus and the D Locus are both involved in silver colored Cockers, some of which almost look solid white.
"C" is considered fully dominant over the lighter, more recessive dilution alleles, but the dominance between the recessive lighter alleles is considered incomplete, with more color dominant over less color, generally. In incomplete dominance if both alleles on a locus are the same recessive allele, the trait that is coded by the recessive will show. But if the locus is heterozygous, the dog will have a "halfway in between" appearance, and only when the locus is homozygous for the dominant allele will the dog show the dominant trait. So one problem with having more than two alleles available on a locus is that it can then be very difficult to decide if a third color is due to a third alternate allele for that locus, or if the third color is due to some type of modifying factor that alters the appearance of only one of the alleles. So again, we are only sketching in the outlines here, and it is often difficult to apply the "rules" to one individual dog.
For instance, the silvery Buff girl pictured here, named Athena, shows several different colors on her face and ears, including what may be some white areas around her nose, and between her eyes--called "white mismarks" in a solid dog--and they look to be part of a "blaze" marking, and she has darker tipped ears. She has a brownish looking nose leather and eyerims, so she may be a chocolate based dog, although there is no chocolate noted in the dogs that are immediately behind her on her pedigree, and the light nose and eyerims could be due to a Blue Dilute gene "d d". Her last litter from a deep red and white male had four solid Buff pups, all differing in shades of Buff, from a deeper red to a lighter cream, and most of them had obvious white markings, and the fifth pup was a deep red and white, with a lot of white. But this litter doesn't really tell us whether or not Athena is a Buff dog or a Clear Sable dog, or the color of her underlying base color, as both Athena and her mate have some Sable in their pedigrees just a few generations back. So our best guess about Athena at this time is that she is a Buff "e e" "ch xch" dog, as explained below, although the darker red pups that she had don't really fit very well with that explanation.
But according to genetic theory an "e e" dog that expresses Buff will fall along the Buff continium as follows:
"e e" "C C" will be a red dog, like our solid red girl, Sparkle, pictured here. But deep solid reds, like Irish Setters, are very rare in Cockers, and red Cockers almost always have lighter "feathering," like Sparkle's light blonde top knot, due to unknown color modifiers, perhaps on the D Locus, which turns red dogs to cream or silver.
"e e" "C ch" will be an orangey colored dog, as in orange Roans in English Cockers, and this color of Buff is much more common in English Cockers than in American cockers. In American Cockers, depending on the depth of tint, the orange colored dog will usually either be called a red or a Buff, as orange is just not a common color name used in American Cockers.
"e e" "ch ch" will be a Buff dog, which is very common in American Cockers. Our retired Buff and white girl named Daisy, shown here, is possibly a "ch ch" dog, but her chocolate base color shows through in her freckles or Ticking on her muzzle. However Daisy does have a rather faint orangy tint to her coat, so she could possibly be a "C ch" dog, as her solid red grand-dam named Dolly is also our Sparkle's dam. Dolly is a very common name for red dogs in American Cockers, as the dam of the very famous red Cocker dog "Red Brucie" was a red girl named Rees' Dolly. Red Brucie was sire to 36 champions, and his youngest son was named "MyOwn Brucie," and was the winner of Best in Show at the prestigious Westminster Dog Show in New York City in both 1940 and 1941. "My Own Brucie" was one of only three American Cockers to win at Westminster.
"e e" "ch xch" will be a cream colored dog, and
"e e " "xch xch" will be a silver dog. We believe that our retired silvery Buff girl named Darlin is probably a "ch xch" dog, and Darlin now lives with her family in Deltona, Florida. We have recently read that the more recessive alleles on the C Locus are temperature sensitive, and that the higher the temperature the lighter the color, and we did notice that our Darlin alternately became lighter and then darker looking occasionally, but we never related it to the outside temperature.
Other C Locus Alleles: In Aussies there is an allele called "ca" which is believed to cause albinism in dogs that are homogygous for it, resulting in an all white dog with pink eyes. And the West Highland Terrier's white color may be due to an allele "ce" called extreme dilution, caused by extreme dilution of tan, while allowing full color of dark noses and eye pigment. And white Dobermans may be caused by a C locus mutation. And it is presently being debated among geneticists whether the C Locus also causes the variations found in the A Locus Sable and/or Tan Pointed colors, or whether other dilution genes are involved. An example of A Locus double dilution would be a black and silver dog, instead of a black and tan dog, but both dogs would be "at at" on the A locus, with another dilution gene making the difference in the tan color. Another C locus allele is called "cb" which is a blue-eyed albino, and this animal has an entirely white coat, called platinum or silver in cats, but with a very small amount of eye pigment, producing pale blue eyes. This allele is called "ca" in cats.
The D locus: The D Locus affects all pigment in the dog, including the eyes, skin, nose, and hair. This is a recessive dilution gene that turns black dogs to grey, brown dogs to blue, and red dogs to cream or silver, as it affects both eumelanin and phaeomelanin. Black dogs are said to have a "blue" cast and yellow dogs are said to have a "peachy" cast. "D D" is dominant and is non-dilute and creates normal pigmentaion. "D d" would look normally pigmented, but carry the dilution gene recessively. "d d" is recessive and dilutes the colors. In some breeds the action of this gene is called "Maltese Blue," and in Great Danes "d d" can dilute the mask and/or stripes in Fawns and Brindles. In black dogs the nose leather, eye rims and lip edges will be dark grey, and some "blue dilute" dogs may have remarkably dark eyes, but this is probably due to the presence of another gene for dark eyes.
The D Locus acts by causing clumping in the pigment granules in the hair, and it often affects skin and eye color. The pigment is uniformly diluted so that black becomes a uniform gray, and brown becomes "Isabella," as it is called in Dobermans--also sometimes called Fawn--and causes the silvery sheen in Weimaraners, but we have read that the D Locus does not affect Tan Points. This dilute gene also causes some common mismarks in Aussies. And the cinnamon color in Chows may be an "ay ay" "d d" genotype, with the dilution gene interacting with clear sable. "d d" may also lighten "Blue Merle" black patches to a dark blue-grey. The black Cocker girl shown above, named Smokie, shows some graying in her solid colored coat, which may be due to D Locus dilution, or she could simply be sun bleached. Smokie is out of our red mahogany Sable-Merle and white male named Max, and our red girl named Sparkle, and this pair of dogs have also produced a Blue Sable and white dog, named Aidan, pictured below, which would be due to "d d" and "ay at" acting together, as the C Locus dilution is not thought to act on black.
Our little Aidan, pictured lying down, just above, with her head just out of the picture to the upper left, is a black based Sable and white girl, who is also from Max and Sparkle, who has diluted down to "blue" instead of mahogany red, like her sire, so she is also probably "d d" on the D Locus. It will probably take a full year, or more, for her coat to dilute to a fully grey or "blue" color. However, we see that she has a very heavy black Shaded Sable overlay, so she may always look partly black and partly grey or "blue."
The E locus, or Extension gene: The Buff gene is not active in a lot of dog breeds, but it produces some of the loveliest colors in Cocker Spaniels. The dominant allele is "E" which allows the original color of the dog to show--either black or chocolate--whether the dog is homogygous or heterogygous for "E." The recessive Buff color is "e e" so Buff must be inherited from both parents. The dog shown here, named Dolly's Cinnamon Stick, is the dam of our red girl named Sparkle, and although Dolly is a solid red dog, and is most probably "C C" on the C Locus, she is still considered a "Buff," as recessive red is "e e" on the E Locus, along with all of the other Buff colors, from orange, to cream to silver, with the different Buff colors being created by what the dog carries on the C Locus, as discussed above. All dogs carry alleles on the C Locus, but in Cockers the C Locus is not seen on a dominant "E E" or "E e" dog, which will be black or chocolate--unless affected by some other gene, like A Locus dilution--because the C Locus is not believed to effect eumelanin, or black pigment. We believe that Dolly is a homozygous solid, recessive red dog--"e e" and "C C"--that is either chocolate based--"b b" as she has a "liver nose" and eyerims, or she is carrying chocolate--"B b"--as her daughter, our red girl Sparkle, has thrown some chocolate puppies.
Melanistic Mask: In the "masked" breeds, such as Afghans, Aussies, German Shepherds, Danes, Pugs, and the Dogue de Bordeaux, the coding for the black mask is "Em" and this gene replaces tan (phaemoelnin) with black (eumelanin) over part of the dog, and in its strongest version can make a black and tan a pseudo-black. And black masking will also displace any tan markings on the face of the dog. This marking is sometimes called the "Superextension Mask" in some breeds, such as Whippets, and represents a dark face, ears, and a darker color down the dorsal line.
Recent research by Schmutz et all has proven that a black mask is formed by an interaction between the "Em" allele on the E Locus, and the A Locus, thus all black masked silvers, creams, and reds must be A Locus Sables and not recessive "e e" Buff dogs. The "Em" allele allows the Agouti protein (Sable) to bind some of the time, causing Sable pigment to be produced on the body, and also allows the melanocyte stimulating hormone (black pigment) to bind on the face instead. An "Em" allele is required for the production of a melanistic mask, so black masked dogs cannot be "e e".
The mask is inherited as a dominant trait, so a dog can be either heterozygous or homozygous for the black mask, and the number of copies of "Em" have no effect on the depth of the color of the mask. Melanin pigment can be black, grey or brown and therefore the term "melanistic" mask includes all of these colors. A black mask will not show up on a solid black dog, and the mask on our solid Blue Merle girl named Zadda, shown just above, shows up because of her silvery Merle coat. Zadda must be "Em e" with the "Em" allele coming from her sire, our Max, and the "e" allele coming from her dam, our red Sparkle. Due to her one litter here we think that Zadda is Tan Pointed "at at" on the A locus, "B B" or possibly "B b" on the B Locus, and we have no idea what she is on the C Locus, as she is not a recessive "e e" Buff, so nothing on her C Locus manifests.
Sable Cockers often have black masks, or at least an unbroken black line running up the center of the muzzle, from the nose to the eyes. The solid Sable girl, named Casey Lynn, pictured just above shows a slight sign of melanistic mask on the top of her muzzle, along with the classic signs of Sable dilution, with the lighter "racoon eyes" and the black Shaded Sable overlay, over a reddish-tan Sable coat. And we do see part of a black mask on Zadda's sire, our Sable-Merle named Max, but his white blaze hides part of his mask, as seen in the picture below.
Brindle: Traditionally it was thought that "Ebr" produces Brindling, such as in Greyhounds, Whippets, Great Danes, and Boxers, but Brindle has recently been discovered to be on another gene called the K Locus. Brindle is not generally known in Cockers at this time, but the writer has seen one picture of a Brindle Cocker from perhaps about 20 years ago. But where present, Brindle will show only in the tan areas of black and tan, while Brindle on black will not show at all. A Brindle dog will show "stripes" of eumelanin-based hairs (black/chocolate) in areas that are otherwise phaeomelanin (red/yellow) based, and the color of the eumelanin stripes may be modified by the regular genes that affect eumelanin, such as the B Locus, which turns black to chocolate, and the D Locus, which dilutes both black and chocolate. Interestingly the skin pigment directly underneath all brindle hairs is black.
A Buff Cocker, or "e e" dog, can only produce phaeomelanin in the hair, but the skin, nose and eye pigment reflects the base color of the dog on the B locus. It is thought that the A Locus hair alleles are overridden by the Buff color, and geneticists say that the "e e" Buff color "extends" over the base color of the dog. Some "e e" dogs have "winter noses," with reduced pigment in the cooler months, and we have noticed this in our Buff dogs. "e e" is sometimes called "recessive red" and is the normal color in some breeds, and Yellow Labradors, Golden Retrievers, and Irish Setters are all presumptively "e e" but the Doberman, Newfoundlands, Flat-coated Retrievers, and Black Labradors are all presumptively "E E." In Cockers reds may be either "Ay Ay," called Clear Sable, "Ay at," red Shaded Sable, or "e e," recessive reds, and crossing Sable reds with recessive E Locus reds can produce unexpected blacks. This happened when we bred our mahogany red Sable-Merle and white boy named Max with our recessive red girl named Sparkle, and quite a few of their pups have been either solid blacks, black and whites, black based tris, black based Merles, or black based Sables. The whiskers may be black in the "Ay Ay" and "Ay at" dogs, and cream in the "e e" dogs.
Buff--designated "e e" in genetic code--is recessive in Cockers, meaning that the pup has to inherit two copies of the recessive allele "e" to become a Buff. "E" or non-Buff, is dominant, and "E E" is homogygous for non-Buff, and cannot carry buff, so will be either a black or chocolate dog, unless it is diluted by another dilution allele like Sable. Our Sable-Merle and white male named Max is an example of an "E E" dog in that he cannot throw a Buff pup, even when mated with a Buff female. (Actually we think that Max is an "Em E" dog in that he shows part of a black mask.) "E e" is not a Buff, but can carry Buff recessively, and "e e" expresses as a Buff dog. But the shade of Buff expressed in the dog is determined by what that particular dog inherited on the C Locus, as described above.
The G locus: This is called the greying gene and it causes the replacement of colored hairs with uncolored hairs with age, somewhat like premature grey hair in humans, and may be related to greying around the head in very old dogs. The gene produces a progressive and uniform greying of the coat and it is dominant. "G G" and "G g" produce greying and "g g" does not. We have not read anything about this gene in Cockers, and we are not sure how one would tell the difference between the action of this greying gene and the dilution gene on the D Locus.
The K locus: We have recently been reading a lot about a newly postulated gene called the K Locus, named after the last letter in the word "blacK," which is now believed to be the locus for dominant black dogs. "K K" and "K k" would be dominant black, and would be epistatic to all alleles on the A Locus, hiding them, with recessive "k k" allowing the A Locus to show through. But dominant black "K K" would in turn be epistatic, or hidden, by recessive red/yellow "e e." And some research with Greyhounds suggests that Brindle may be on the same locus as dominant black instead of on the E Locus as suggested by Little. The interatction of the dominant black and Brindle alleles would be as follows: "K"is dominant black, "kbr" is brindle and "k" is normal, allowing the A Locus to show through. Thus a "K K", "K kbr", or "K k" dog would be dominant black (or chocolate); a "kbr kbr" or "kbr k" dog would be a Brindle; and "k k" is normal. But we will reserve writing anything more about this gene until we understand it better.
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