Suwannee Cockers
The Place for Natural Merles and Sables
COAT COLOR AND MARKINGS GENETICS IN AMERICAN COCKERS--Page 3
The M locus: This refers to the Merle gene, and not a lot is known about this gene, or even if it is just one gene, or perhaps a complex of genes. But very recently a group of genetic researchers have announced that they have found what they consider to be a genetic marker for the Merle marking, and they are now marketing this gene test in order to discover if a dog is a Merle or not, as Merle can be hidden under several other colors, including Sable, buff and even black. And for convenience sake it is considered one gene when speaking about it genetically, with "M" representing the Merle allele and "m" representing the non-Merle allele. However, despite this convention, Merle is not a dominant gene, but is considered "co-dominant," as it does not affect all of the dog's colored areas, and sometimes a dog will be carrying "M" but will not have one Merle hair on its body. These dogs are considered "hidden" or Cryptic Merles, and are considered rare. However, we have had two hidden or Cryptic Merles, so we are not exactly sure how really rare they are. And as with other genes, Merle can also be epistatically hidden by other dilution genes like Sable and Buff.
The Merle marking is usually found in certain herding breeds--Shelties, Collies, Aussies, Border Collies, Welsh Corgis--and Harlequin Great Danes, Catahoula hounds, and Dachshunds--and in the past 25 years or so has "appeared" in many other breeds, including American Cockers. Many Cocker breeders say that the gene was "introduced" into Cockers from another breed, but what they really mean is that they believe that Cockers were homozygous for "m m" or non-Merle, until the "M" allele for Merle was introduced from another breed. However, it is entirely possible that the Merle gene in Cockers was somehow "switched on" in just one individual dog, and that would be enough to "introduce" the Merle allele into the breed. After all this would be how the gene mutated in the first place, so there is no reason to think that it couldn't happen again. We will never know for sure, and after five generations of registered AKC breeding, a dog is considered to be a "pure bred," so all AKC Merle Cockers are now "pure bred," even though the national Cocker breed club does not recognize the Merle marking in American Cockers, and the AKC will not list them as Merles on registration papers.
At the time that this is being written the national breed club is considering the "problem" of Merles in American Cockers, and breeders are awaiting their decision. Some Cocker breeders absolutely hate Merle American Cockers and would like to see a suspension of AKC registrations for all Merle Cockers, or at least shuffle the Merles onto a "Z" list, much like the White Dobermans are treated by the Dobbie breed club. But the Merle gene has been researched back in Cocker pedigrees for at least 25 years, and a further complication is that only about half of puppies born to Merle dogs are Merles in the first place, as the Merle gene is not completely dominant, plus there can obviously be hidden or Cryptic Merles, and no one knows how many Cryptic Merles there are in American Cockers. One of our males is a Cryptic Merle, and we have certainly bred one other Cryptic Merle pup so far--so the whole question of Merle American Cockers is presently "up in the air."
The Merle gene produces very irregular patches of diluted color in the base coat of the dog--black or chocolate, and Merling has little or no effect on phaeomelanin. One writer has likened the effect to "throwing bleach on the dog" and the diluted Merle pattern is apparently entirely random. The Merle gene dilutes black dogs to grey, called "Blue Merle," and chocolate dogs to tan, with variations of tone according to the base coat--there are red Merles in Aussies--but the dominance is considered incomplete, because not all of the dog's coat is affected, and thus neither allele is dominant over the other. Merle has also been called "overdominance" where one desires the heterozygous state, "M m," and the heterozygous state looks different from either of the other two states--in this case "M M," which would be a double-merle, and "m m" which is a non-Merle. "M m" produces "Blue Merle and Tan" in Tan Pointed "at at" dogs and Sable-Merle in Shaded Sable "Ay at" and Clear Sable "Ay Ay" dogs.
There are also hidden or Cryptic Merles, as mentioned above, where the Merle gene "M" is present, and can be passed on to puppies, but the dog does not exhibit any Merling at all. Sable can also hide the Merle gene somewhat, or completely, and Sable-Merles are an increasingly popular coat pattern in several breeds, and are being shown, and winning, in the Sheltie ring. We believe that the black and white puppy shown in the two pictures directly below, named Banks, is a "hidden" or Cryptic Merle, in that as a puppy he did not have one Merle hair on his body, but his one blue eye and his partly pink nose indicate a large degree of dilution. And since his sire is our Max, who is also a Cryptic Merle, we believe that this little guy is also a Cryptic Merle.
Most Merle dogs are heterozygous for merle--"M m"--and all non-Merle dogs are "m m." Double merles are "M M," and this is a very undesirable gene combination, as one quarter of the litter from mating two regular "M m" Merles together will be "M M," and these double Merle pups may have incomplete development of the ears and eyes, due to a reduced amount of melanin during embryonic development, and the Double Merle "M M" pups may be blind, deaf, or both, and even lack eyes. Other abnormalities may accompany the double Merle allele, and pups may be born dead or die shortly after birth. These defects have been documented in several Merle breeds, especially in Aussies and Border Collies, but we have recently read that some Dachshund breeders have successfully bred Merle to Merle in their breed with no abnormalities at all, so we are not sure if these defects are truly due to the Merle gene, or to some accompanying gene, and more research needs to be done. However, just to be sure, we do not breed Merle to Merle.
Therefore responsible breeders do not breed Merle dogs together, and it is important for Merle breeders to know their dog's pedigrees. This is why it is so important for Merle Cockers to be recognized as Merles by the AKC--and not as Roans--so that the Merle gene will be readily apparent in the pedigree. We currently use double "Z's" in all of our Merle dog's names, so at least we can keep track of our Merle lines.
We personally believe that the Merle "gene" is actually a complex of genes, and that other dilution genes may be involved, such as the genes that create Roaning or perhaps Maltese Blue. In Aussies it is believed that just the lightening of the eyes in Merle dogs involves at least two, if not three alleles, which are different from the coat color and markings alleles, and having light eyes does not always mean that a dog has the Merle gene--just that some type of dilution allele is involved. And there is a recessive gene in some lines of Aussies that does produce blue eyes independently of Merle, and these eyes are split geometrically, not marbled. It can produce a dog with two blue eyes, one blue and one pigmented, or irises that are split. And a blue eyed Merle dog may have this recessive blue eyed gene, and not have blue eyes due to its Merle gene.
And in fact many Merle dogs do not have light eyes at all, but have dark eyes, or one of each, and we get many more dark eyed Merle pups than blue eyed ones, which factors out at the present time to only about 8% of our dogs having two blue eyes. And Siberian Huskies have blue eyes that are not believed to be related to the Merle coat marking gene at all, and this may be true in other breeds as well. For instance, we have recently seen pictures of Whippets with one blue eye and one dark eye, which is an instance of "somatic mosaicism," which is an effect of a mutation in one cell at the two-cell stage in embryonic development of the puppy. This may give rise to two different cell lines in a single puppy, each of which has a different phenotype, such as two different color eyes in the same dog. But Merle is not believed to be present in Whippets.
We believe that the Merle gene is especially showy in the long American Cocker coat, and we are endeavoring to learn more about this fascinating coat marking. However, we recognize the dangers involved in uneducated breeding of Merles, and this is one of the many reasons that we place all of our dogs into pet/companion, non-breeding homes.
For more discussion of Merle Cockers and a lot more pictures of Merles, you may go to our page that is devoted only to the Merle marking, called About Merles, but if you go there now you will have to come back to this point through the "Articles" page.
The P locus: This is a very rare dilution gene, and we have not been able to find much written about it, or what breeds of dogs are involved. We have read on a Labrador Retriever website that the P Locus is called the "Pink Eye" gene, and that it causes black to be diluted to blue, liver to yellow, and causes "pink eyes." "P" is the dominant normal allele of the gene, and "p" is the recessive dilution allele.
The R locus: Roans are almost as controversial in American Cockers as the Merles, but at least most Cocker breeders will admit that Roans are a traditional Spaniel color and/or marking, and a very few Roan dogs are shown in the American Cocker show ring. But ironically, that is just the problem, as the marking is so much associated with English Cockers that some American Cocker breeders either dislike it or don't even recognize it when they see it. And we have even heard stories about judges who have erronously dismissed Roans from the ring as a mismark, as they don't actually recognize the marking when they see it. Also there is some controversy as to whether there is really a Roan gene, or whether Roaning is just extreme ticking. So we searched the internet for some answers about Roan Cockers, especially as all of our Merle dogs are erroneously listed on their pedigrees as Roans.
Thus far there is no DNA test for spotting nor any gene confirmed to cause spotting in dogs.
This is a quote from Sheila Schmutz PhD, a very well known Canadian dog genetic researcher. And Schmutz goes on: "Ticked dogs also typically have Roan areas. Roan was inherited as a heterozygous genotype at the MGF locus in cattle but plated (dogs with large dark spots) and ticked dogs have identical MGF sequence. Little (1957) suggested that roan could be caused by a separate gene. It might be said that merle dogs also have roan areas."
Thus there is a lot of confusion and controversy about the different spotting markings in dogs--variously called Roaning, Belton, and/or Ticking. Some Cocker breeders say that Roaning is white hairs gradually appearing in the dark areas of Cockers, and Ticking is dark spots appearing in the white areas. But other breeders say that Roaning is just heavy Ticking. So we decided to look at the English Cocker Roans, as after all, this is the breed from which American Cockers came, and Roan is the marking most associated with English Cockers. The following is from an English Cocker site, and we have a link to this site on the first page of this color genetics section:
The factor for "roaning" is the most dominant of the particolour patterns as we know them. It seems to be a gene with a wide spectrum of variety in how it is expressed. Some roans are quite deep with a high proportion of black (in the blues), liver (in the liver/chocolate roans), orange (the counterpart of red) or lemon (the counterpart of golden) hairs compared to white hairs present in the roaned areas of the skin. There seems to be every combination of proportion of these mixed hairs right from very, very dark roan down to the lightest of roans in all of these colours where the white hairs are present in much higher proportion than the coloured hairs on the roaned areas of the coat. In general the darker roans are dominant over the more lightly marked roans.
The areas of black (or liver/chocolate, orange or lemon) patching usually will cover the ears, both sides of the skull and around the root of the tail. There may be patches of colour anywhere else over the neck, legs, body and hindquarters. These markings may be partially or wholly absent with roaned areas in their place. The head may present as solid black but the most usual form is for a flash or blaze of roan to cover the majority of the muzzle and run up between the eyes, over the stop to the back skull. At this point, in the darker roans it would be usual for the head markings on the side of the skull to join over the occiput and in the lighter roans (or at least those light roans with few body patches) it is often the case that the blaze runs over the occiput with either no spot or a spot isolated from the other skull markings. All of these variations are considered correct.
And accompanying the above paragraphs are pictures of solid black patched dogs, with areas of white interspersed with dark spots in various intensities. Thus, from our research in English Cockers, we believe that a Roan dog is a parti dog with the white areas having a mixture of both dark and white hairs--more intensely than in what we called Ticked dogs--and the solid dark areas of the coat are totally dark, unlike the Merle gene, which affects the dark areas of a parti coat. We have never seen a solid Roan, as apparently there must be some white areas for the Roaning to occur, and this is backed up by the English description of a blaze usually being present up the forehead of the Roan English Cocker, as a blaze is usually found only in a parti dog--or sometimes in a mismarked solid Cocker. And if the dog is black based, and the black part of the coat is diluted to a grey color, then the color is called "Blue Roan," which is a very popular coat color and marking in English Cockers.
Thus there is some dispute among geneticists as to whether Roaning is really just extreme Ticking, or whether it is an actual separate gene locus, and with Roan now being a rather unusual marking in American Cockers, there are not a lot of Roan Cockers to observe. One sees many English roans, and some American Roans, with Tan Points, and a Blue Roan with Tan Points is an especially striking looking dog. But the listing of American Cocker Merles as Roans is not doing either marking any good, and the confusion with the Roans is another reason to list American Cocker Merles correctly on their pedigrees.
Our chocolate tri girl shown here is named SunCatcher's Suzy Q, and the owner of her sire thinks that Suzy Q is indeed a Roan American Cocker, as can be seen by the mixture of chocolate and white hairs in her longer coat on her sides--called a "skirt"--as seen below. Suzy Q also has the lighter nose and eyes that often come with the chocolate dilution allele on the B Locus in Cockers, and her light eyes probably have nothing to do with the Merle gene, but are most likely due to the Chinchilla gene on the C Locus, as Suzy Q does have one very light Buff and white littermate. Suzy Q is a beautifully put together Cocker, with a nice head--not too extreme--a great stance with excellent movement, a nice long neck and a sloping topline, and a rather boxy body. She is altogether a modern Cocker, but one who looks as if she could actually carry a bird in her mouth, as her muzzle is not too plush or too smushed. She has nice large eyes, but they do not bulge out of her head, and her chocolate color and lighter eyes give her a very sporting look indeed! At the time that this is being written Suzy Q's sire is being shown in the Cocker ring, and is about half way toward his Championship.
"R" is considered the dominant Roan allele, and "r" is considered the recessive non-Roan allele. However, as far as we know, the Roan gene has not actually been found in dogs, and some geneticists think that Roaning is just extreme Ticking in the white areas of the coat. But presuming that there is an actual Roan gene in dogs, it would only take one dominant Roan allele for Suzy Q to be a Roan, and she could be carring a non-Roan allele also, and thus be heterozygous "R r" on the R Locus.
The S locus: This is the "spotting" gene, or "white factored" gene, and it too is a continium from a totally colored dog, which is dominant, to an all white dog. However, all of the alleles on the S Locus are incompletely dominant, with the resulting white spotting pattern being "in between" the two alleles in a heterozygous dog. But in any two heterozygous pairs of alleles, the more dominant allele is usually slightly more evident, making determining the exact alleles involved in any white spotted dog rather difficult to discern. Mr. Darcy, the solid chocolate Sable dog, shown here at about three months old, is a heterozygous dog on the S Locus, probably "S si" with just a few white markings on his chin, his chest, and a small white spot on the toe of one foot.
The following four alleles are thought to be active in American Cockers on the S Locus and are listed in the order of most dominant to most recessive, although the incomplete dominance is the reason that many Cocker breeders do not mix solid and parti dogs, tryng for a homozygous "S S" dog with no white mis-markings. However, if the various patterned dogs within a breed are not mixed occasionally, then the different markings will veer off from each other in type, and this has happened quite a bit in English Cockers, with the solids sometimes looking quite different in type from the partis. We do mix up all of our colors and markings, striving for the best tempered dog, and let the spots fall where they may, which makes for some very interesting patterns and colors, and creates very individually marked dogs. We also feel that genetic diversity is healthier as "the measure of the amount of heterozygosity across all genes can be used as a general indicator of the amount of genetic variability and genetic health of a population." This is a quote from an introduction article about "population genetics," on the National Biological Information Infrastructure (NBII) website and reflects our feelings that within a limited gene pool, such as in a purebred dog, the more genetic diversity the better. But back to white spots on dogs.
"S" is a dog that has little or no white spots--less than 5%--and this dog is usually called a "solid" dog. "S" is the dominant allele, and a dog that is heterozygous "S" with any of the other spotting alleles will appear to be a solid dog, but will carry white spotting recessively, and may itself have a small amount of white markings. But a dog that is homozygous "S S" cannot carry any recessive spotting genes. AKC American Cockers are shown in three color classes, two of which are solids: the first is solid black, and the second is called "ASCOB" for Any Solid Color Other than Black. The third class is for partis, or white spotted dogs. A small bit of white is considered acceptable on the chest in solid dogs, but other "white markings" that make up less than 10% of the coat of the dog are disqualifications for a solid dog in the ring. However, as the melanin is laid down last in the fetus on the chest, muzzle and nose, many solid colored Cockers have white markings that aren't necessarily genetically related.
"si" is often called "Irish spotting" and a dog that inherits "si si" produces the "normal white pattern" of the herding breeds, with white on the paws, tail tip, the chest and the front of the neck. "si" can carry the more recessive spotting genes, but cannot carry the dominant "S" solid gene, and Irish marking is traditionally found in Spaniels and Cockers, as well as the herding breeds, although not in great numbers. An "si si" dog should have about 25% of its coat white, and may or may not have a complete white collar or shawl, which is a white ring around the neck. Our Shaded Sable-Merle and white dog named Max, shown above, is technically a parti, and not-Irish marked--because he has some white incursions into his mantle, but he is very close to being an Irish marked dog, and he is may be "si sp" on the S Locus, or possibly even "si sw" (called "white factored") as he seems to throw parti dogs that are either somewhat Irish marked, or are very open parti dogs, with lots of white. Interestingly enough two "si sw" dogs bred together will produce 25% "si si" dogs which will probably not have a collar, 50% "si sw" white factored dogs which will probably have a collar, and 25% color-headed whites--"sw sw". The term "Irish" comes from a type of mice used in early genetic research that had these white markings, which are also sometimes called "Dutch" markings.
"sp" is the most typical white spotting allele in Cockers, and produces variable amounts of white markings all over the body, in random patterns, with the dog being about 50% white. When breeding partis many Cocker breeders aim toward this "half and half" marking, although some other breeders really prefer a more "open" dog with more percentge of white, but a dog that is more than 90% white is disqualified from the Cocker ring. The black tri dog shown here, Dee-Lyn's Phantom of the Opera, who is the sire of our red Sparkle, is probably "sp sw" as he has quite a bit of white, but not enough white to be considered a "color head" or "sw sw" dog.
"sw" is the "color-head" or extreme white allele, producing an almost all white dog, with just a few color patches, often limited to the ears, around the eyes, and/or on the tail. This is the most recessive of the white spotting alleles, and dogs that are homozygous for "sw" can only carry this allele. Certain breeds, like Papillions, have quite a few "sw sw" dogs.
The white spotting patterns are often difficult to distinguish due to the incomplete dominance in the series, and for instance an "S sw" dog can look almost identical to an "si si" dog, and all "flashy" boxers are "S sw" and not "si si". And when one flashy Boxer is bred to another flashy Boxer 25% of the pups are solids, 50% are flashy, and 25% are color heads, so in this instance solids are coming from two white spotted dogs which is supposedly impossible! But it all makes sense once one plots out the various alleles involved and thus sees that two "S sw" dogs bred together will indeed throw solids. Thus even such a simple appearing marking as parti can often prove to be rather complex and difficult to understand, and it is only by having several generations of dogs to actually look at, and notice which dogs throw what, that one can even begin to figure out what is happening with the coat color and markings genetics that is involved.
The "T" locus: The T Locus determines whether there will be small dark spots in the white areas of the dog, called "Ticking," and also sometimes called "freckles," and this picture of our retired Buff and white girl named SunCatcher's Dixie Daisy, shows that the color of the ticking usually reflects the base color of the dog, which in Daisy's case is chocolate. Daisy is more of a "sporting type" Cocker, with a shorter "sport coat" than most American Cockers, and she has less stop and the longer muzzle of the older hunting type of American Cocker. There is absolutely nothing in Daisy's pedigree to indicate any Merle in her background, and she is simply a throwback to the older type of Cocker, as she has a long line of show dogs behind her. "Genes don't disappear. They hide."
"T" is dominant, and "T T" is homozygous and will always throw ticking. "t" is recessive, and homozygous "t t" produces clear areas of white, and should have no ticking at all--like our Blue Merle, tan and white girl named Zieara, shown here--and heterozygous "T t" should have some amount of ticking. But ticking depends on the dog having some white areas to show up against, and solid colored dogs with no white areas are epistatic to ticking, meaning that the solid allele on the S locus hides the ticking allele on the T locus. Daisy has a lot of ticking in all of her white areas and is probably "sp sp" on the S Locus, or Spotting gene, and "T T" on the T Locus, or Ticking gene. Zieara is probably "si sp" on the S Locus and "t t" on the T locus, as she had an almost intact mantle or saddle over her back, but absolutely no ticking on her white areas. Fiona, the heavily ticked black and white girl shown directly below, is probably "sp sp" on the S Locus, and "T T" on the T Locus, while her full brother, ZuZu, is a "clear," which shows that both of their parents are probably "T t" as they throw both heavily ticked and totally clear puppies.
Often one has to have puppies before the breeder can really tell what a dog is carrying on the various gene loci, and sometimes even then one can't really be sure, but is just making "educated guesses" about the genetics involved.
The W Locus: We have read very little about the W Locus, but it supposedly dilutes grey merle areas to white. "W" is the dominant dilution allele, and "w" is the non-diluting recessive allele.
Most of what we have written above has not been proven by genetic tests, but is believed to be true by years of observation by breeders. We have mostly discussed these genes as they might affect Cockers, and have only briefly touched on some of the other breeds, but Cockers have such a variety of colors and markings available that they offer plenty of room for thought and contemplation as well as speculation. In future years the dog genome will be complete, and a lot of speculation about coat color and markings genetics will become known fact. But until then, breeders have to rely on the traditional explanations from the published genetics books and their own observations over time.
Below we have listed some other coat color and marking terms that one might run across in discussions of dogs, and these terms mostly refer to breeds other than Cockers.
Belton: intermingled colored and white hairs.
Bicolor: a coat of two distinct colors, usually called parti in Cockers. The two pups above are from a litter from Max and a now retired black tri Roan girl named Dottie, and the black and white pup on the left, named Gus, is a typical bicolor (dominant black), with only two colors. But the mahogany red Sable and white girl on the right--possibly diluted--named Bridget, turned out to be a Roan, a Sable, AND a Merle, and eventually she had lots of little spots in both her colored and her white areas! Her partly pink Butterfly nose shows that she has some extra dilution.
Brindle: an even mixture of dark colors with lighter colors, such as a striped tiger-like coat.
Domino: reverse facial mask--in Afghans and Salukis a light muzzle with a dark widow's peak, and dark on top of head and ears.
Fawn: color of a newborn deer.
Grizzled: a Roan pattern that is usually a mixture of black, bluish-gray, iron gray, or red with white.
Harlequin: blue or black patches on white.
Hound colored: black, tan and white with a black saddle.
Lion color: tawny tan coat color with darker shading, as seen in Ibizan Hounds
Piebald: black and white or two other colors in patches. Our red and white boy, named Beau, pictured just above, could be called piebald, or bicolor, but this two color marking is called "parti" in Cockers.
Saddle: a large, solid, dark patch over the back. Although rather rare, this coat pattern is occasionally found in American Cockers.
Spectacles: dark markings around the eyes. In Cockers this is also called "Egyptian Eyes," and our Sable-Merle and white male named Max, shown above, has this marking.
Tricolor: a coat of three distinct colors, such as black, tan and white or chocolate, tan and white, often found in American Cockers. Our Blue Merle, tan and white girl named Zieara, shown above, was a tri color.
Wheaten: pale yellow or fawn colored.
Designed and Maintained by
BIG OAKS DESIGN
BigOaksDesign@Gmail.com
Copyright Suwannee Cockers 2004-2007
