Defining Colors
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Its important to start with the basic sold colors of a dog. This Is the B locus. All dogs have a base coat of either Black or Chocolate (Brown). You can typically determine by the eye if they are Black or Chocolate based on the pigment of their nose. Genetically testing your dog is always best to determine proper genetics. If there are no other genes in the genetic makeup of the Black or Chocolate dog, you will see a solid Black or Chocolate dog. Black is a dominant color gene, so it requires only one copy of the Black gene to give you Black. Chocolate is recessive and requires two copies of the gene and therefore both parents need to carry Chocolate. The gene that determines Black or Chocolate is the B locus. B/B or B/b = Black (remember that dominant colors are capitol letters) and b/b = Chocolate (Brown).
The colors white, cream, apricot and red are all produced by the same gene. This is the E Locus. It is a recessive gene so you need two copies of this gene for it to show in their coat. These dogs can have either Black or Chocolate pigmentation. This gene gives a range of shades within it, going from white to red. So if I breed a white to a red, I can get a range of colors in between. (It is also important to note, that the K locus and A locus will not be expressed if a puppy is genetically e/e. Remember that lower case is recessive.) E/E or E/e = No White, Cream, Apricot or Red and e/e = White, Cream, Apricot or Red.
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When it comes to dogs, sometimes colors and patterns can be breed specific. For example, the harlequin gene in most commonly found in a Great Dane. This is a gene whose color pattern results in black patches of color on a white base. Its important to understand that all harlequin coated dogs carry one copy of the merle gene. However dogs without the Merle gene or color pattern can carry the gene for harlequin. The same can be said for a brindle gene. It is not found in every breed and certainly not every doodle.
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Phantom Brindle and Sable color is the result of two genes working together. The first gene is the K locus. There is a dominant gene, Kb, and a recessive gene, Ky. Kb is a blocking gene that does not allow the expression of the A locus. A locus is the second gene needed to produce phantoms/sables. Therefore if you have even one Kb gene in a line, the A locus can not be expressed at all. This holds no matter what the genes are on that locus. The Brindle gene is believed to be found on the K locus and only needs one copy to be expressed. Kb/Kb, Kb/Kbr or Kb/Ky = No expression on A locus. If you end up with Kbr/Kbr or Kbr/Ky = Brindle Expressed (not all genetic testing companies test specifically for this and it can be controversial). Ky/Ky = Expression of A locus allowed.
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The coat colors that show on a Solid Black and Chocolate (brown) are determined by the A locus. This tiered system is as follows: Ay/Ay = Sable, Ay/At = Sable Phantom, At/At or At/a= Phantom and last a/a = Solid Colored.
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Parti The S locus controls the placement of the white in a dog. It also controls how much white is in a dogs coat. We call this Parti. It is white markings on any other color already noted above. Parti is a recessive gene. This is a color that you wont typically see in F1 generations. However you can get parti’s in F1b or above generations. Remember that Solid colors are dominant and parti colors are recessive. S/S or S/sp = Solid Color and sp/sp = Parti Color. The S Locus also has untestable sub-loci, so some aspects of how the S Locus affects color are still unclear, perhaps even unknown. As a general rule however, dogs with SS will be solid or may have abstract patterns (areas of white on the face, chest & paws). This Abstract gene can be seen often in F1 Bernedoodles. Ssp will typically have 50% or less white such as abstract and tuxedo patterns. Last, spsp will have 50% or more white. These are typically considered "parti". As a general rule, parti is more than 50% white and will often have a broken color pattern down the back. There are however, exceptions to this.
Abstract colors are often a result of a dog carrying one parti gene. Its important to remember that not all abstract carry parti and not all parti carriers have abstract markings.
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The D locus in dogs is a dilute gene. Silvers are thought to be caused by the D locus and that they are a recessive gene. This can be controversial also. A dd locus will result in a modification of the base color of the dog the D locus has. This turning a black dog silver, etc. There are varying degrees of sliver. The D gene will produce blues, charcoals and lilacs.
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Merle Now that we have discussed most other colors, we can now talk about the Merle pattern on a dog. The merle gene is extremely complex and just as controversial. Merle is a coat pattern with varying shades of blue/black or brown/red. It comes from the Allele M. In order to get a mere allele you need a dominant and recessive trait to produce this pattern. This is the merle allele (M) and one copy of the non-merle allele (m). The merle (M) allele is an incomplete-dominant (sometimes called a semi-dominant gene as well) gene, meaning it only takes one copy of the M allele to produce a merle. This mean that every merle dog has one copy of the merle allele (M) and one copy of the non-merle allele (m). In other words, every merle dog has an Mm genotype and every non-merle dog has an mm genotype. The term incomplete dominant means that one allele does not completely dominate another. When it comes to the merle gene, depending on which two alleles are inherited by each puppy, it can create an intermediate expression or a completely distinct pattern. There are now 4 Merle Scales. I have listed them below. Each scale rate the length of these Alleles differently.
Depending on the scale used, there are either two, four or six different Alleles for M. Mc, Mc+, Ma, Ma+, M, Mh. Each Allele has a numeric value to gauge the level of pattern shown on the coat. This is the length of the Allele. The two distinct differences between the different scales is that the first 3 when compared with the “langevin et al” scale, the 4th is based on phenotype AND breeding results. The breeding results include HOMOZYGOUS result. The first 3 scales have only included heterozygous dogs in their research.
m Non-Merle Wild Type
Mc Cryptic Merle 200 - 230 bp
Mc+ Cryptic Merle + 231 - 246 bp
Ma Atypical Merle 247 - 254 bp
Ma+ Atypical Merle + 255 - 264 bp
M Merle 265 - 268 bp
Mh Harlequin Merle 269 - 280 bp
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#1 - scale includes only 2 alleles, Mc and M, from a paper published in 2015, "Milushova et al". The length of the two alleles was set using the old testing method and based on phenotype. Dogs 252 bp and below were most likely to express no Merle pattern. Those 253 and above either had a noticeable Merle pattern or where starting to show signs of an unusual coat shading or faint pattern.
#2 - scale as set by Paw Print Genetics "Ballif et al" including 4 alleles, Mc, Ma, M and Mh based on phenotype, with Ma starting at 247 bp which was a number already set by Biofocus with the help of Dr. Helena Synková in 2011. This leaves the Mc extending as far as 246 bp.
#3 - scale from the "Murphy et al" (Dr Clark) paper including 4 alleles with Md (equivalent to Ma) starting at the same number as scale #1's M allele of 253 bp based on phenotype. This leaves a gap between Mc and Ma with Mc possibly extending to 252 bp. M and Mh overlap. NOTE - this paper uses T length numbers, I have converted them to base pairs for easier comparison.
#4 - scale as defined by "langevin et al" with 6 alleles - Mc, Mc+, Ma, Ma+, M and Mh
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Here is the different Merle Allele length scales.
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These are the Merle Phenotypes:
m/Mc
No Merle pattern, no change to coat color or pigment shading. No eye color change. No pigment is deleted to white.
Mc/Mc
No Merle pattern, may express as no change to coat color or pigment shading. Alternatively, there may be a slight change to coat color – pigment may express as faded or off-color or a slight brownish hue may express that is not related to b/b, especially for long coated breeds. No eye color change. No pigment is deleted to white.
m/Mc+
No Merle pattern, no change to coat color or pigment shading. No eye color change. No pigment is deleted to white.
Mc+/Mc+
No Merle pattern, may express as no change to coat color or pigment shading. Alternatively, there may be a slight change to coat color – pigment may express as faded or off-color or a brownish hue may express that is not related to b/b, especially for long coated breeds. No eye color change. No pigment is deleted to white.
m/Ma
No Merle pattern, may express with no change to coat color or pigment shading. Alternatively, may show a diluted coat expression even when d/d is not present and/or a brownish hue may express that is not related to b/b. May express with a lighter undercoat especially on longer haired breeds. Lighter shaded areas may be visible on ears, neck, under tail and tail area. Blue eyes can be expressed. No pigment is deleted to white.
Mc/Ma
No Merle pattern, may express with no change to coat color or pigment shading. Alternatively, may show a diluted coat expression even when d/d is not present and/or a brownish hue may express that is not related to b/b or express with a lighter undercoat especially on longer haired breeds. Lighter shaded areas may be visible on ears, neck, under tail and tail area.
Blue eyes can be expressed. No pigment is deleted to white.
Ma/Ma
Most often diluted in color even when d/d is not present and/or a brownish hue may express that is not related to b/b, more diluted background shading with smaller and fewer areas of darker spotting.
Blue eyes can be expressed. No pigment is deleted to white.
m/Ma+
Merle pattern is muted, not crisp and clear or as well defined as some breed standards may require, most often diluted in color even when d/d is not present and/or a brownish hue may express that is not related to b/b. Alternatively, some dogs may express with no Merle pattern, no dilution and no change to coat color or pigment shading. Blue eyes can be expressed. No pigment is deleted to white.
Mc/Ma+
Merle pattern is muted, not crisp and clear or as well defined as some breed standards may require, most often diluted in color even when d/d is not present and/or a brownish hue may express that is not related to b/b. Alternatively, some dogs may express with no Merle pattern, no dilution and no change to coat color or pigment shading. Blue eyes can be expressed. No pigment is deleted to white.
Mc+/Ma+
Often diluted in color even when d/d is not present and/or a brownish hue may express that is not related to b/b, more diluted background shading with smaller and fewer areas of spotting. As the base pairs of Ma+ progress closer to M, a more noticeable Tweed patterning may be present, larger areas of solid pigment may show.
Blue eyes can be expressed. Some pigment may be deleted to white as the base pair numbers of Ma+ progress closer to M.
Ma+/Ma+
Most often diluted in color even when d/d is not present and/or a brownish hue may express that is not related to b/b. More diluted background shading with smaller and fewer areas of spotting. Tweed patterning may be present. Blue eyes can be expressed. Pigment may be deleted to white.
m/M
Classic Merle pattern – random areas of the coat are diluted to a lighter pigment, creating a combination of areas consisting of a diluted color mixed with areas of full pigmentation. Blue eyes can be expressed. No pigment is deleted to white.
Mc/M
Random areas of the coat are diluted to a lighter pigment, creating a combination of areas consisting of a diluted color mixed with areas of full pigmentation. Tweed patterning may express. Blue eyes can be expressed. No pigment is deleted to white.
Mc+/M
Random areas of the coat are diluted to a lighter pigment, creating a combination of areas consisting of a diluted color mixed with areas of full pigmentation. Tweed patterning may express. Blue eyes can be expressed. Some pigment may be deleted to white.
Ma/M
Often referred to as “Patchwork” with large areas of solid pigment mixed with areas of more diluted background shading with smaller and fewer areas of darker spotting. Tweed patterning often expressed. Blue eyes can be expressed. Some pigment often deleted to white.
Ma+/M
Most often diluted in color even when d/d is not present and/or a brownish hue may express that is
not related to b/b. More diluted background shading with smaller and fewer areas of spotting.
Extended white out of normal Irish Spotting pattern – up legs, past shoulders, white head often noted (seemingly not related to the “white-head” gene). Blue eyes can be expressed. Pigment can be deleted to white.
M/M
Random areas of the coat are diluted to a lighter pigment, creating a combination of areas consisting of a diluted color mixed with areas of full pigmentation most often mixed with varying amounts of white. Blue eyes can be expressed. Pigment can be deleted to white.
Mh
The Mh allele has a broad range of phenotypes with 2 expressions that are very recognizable.
#1 - “Minimal Merle” - a large percentage of the body features solid colored pigment with only small random areas of Merle patterning. Individuals may also express extended white out of the normal area of the typical Irish Spotting pattern – this may include a large white collar, white up legs past the elbow, white past shoulders extending onto withers and white on the belly extending up the side. This extended white is sometimes associated with S/sp - (Piebald Carrier), however many m/Mh dogs with this type of white pattern have tested as S/S.
#2 - The more classic pattern that is often referred to as “Herding Harlequin” - Random diluted areas of Merle pigment are deleted to white, leaving solid patched areas that may be Tweed patterned including different shades. Some Merle areas may remain. The extended white patterning mentioned in description #1 may be present but is less noticeable due to the deleted white areas on the body.
#3 - Some dogs may express more as m/M, yet are still able to produce offspring with a phenotype as described above in example #1 and #2 - these offspring have inherited the same length of base pairs as the parent and yet express in either of the 3 ways presented here.
Mc/Mh, Mc+/Mh, Ma/Mh, M/Mh and Mh/Mh allelic combinations are phenotypically indistinguishable and present one homogenous phenotypic group.
Of note, M/Mh and Mh/Mh may express with a greater percentage of white over the body.
*Scale1. (Murphy Et Al) Base pair ranges that correspond to the four varieties of the merle phenotype: Note, there are gaps between cryptic/dilute and dilute/standard
cryptic (212 - 242 bp), dilute (253 - 261 bp), standard (265 - 273 bp), and harlequin (268 - 292 bp).”
*Scale 2. (Paw Print Genetics)200 – 246 Cryptic - Most cases are non-merle but in rare cases may have very small merle patch(es) or subtle color anomalies.
247 – 264 Atypical - Most cases show a significant shift from normal coat color often giving a diluted color, show reddish undertones, or have an otherwise atypical merle appearance.
265 – 269 Classic - Most cases show classic merle with a significant amount of merle color and pattering, although some cases may only
show a minimal amount of merle.
270 – 280 Harlequin Most cases display patches of multiple shades of the same or different colors without white (tweed) or with white (harlequin) and are often referred to as patchwork.
Their scale of “Cryptic” 200 - 246 bp includes both our Mc and Mc+ alleles, which can express different phenotypes when homozygous and also when inherited with different length alleles.
The Mc allele as set with Vemodia at 230 bp will not delete pigment to white when combined with M.
However when Mc+ is combined with M there is the possibility of pigment being deleted to white in
the Merle pattern which some breed standards do not allow and could be a concern for
impairments.
Two Important distinctions comparing PPG to Langevin here are m/Ma does not create a Merle pattern whereas m/Ma+
can.
Ma/Ma will not create white in the Merle pattern whereas Ma+/Ma+ can delete pigment to white.
There can also be anomalies when it comes to genetics. Sometimes small area of that presents on a puppy can be a pigmentation and in fact is not minimal merle. This is caused by the Mc allele. This phenotype is commonly seen in breeds where "Whitehead" is common.
Double Merles…. When a merle is bred to another merle, you get two merle alleles (MM). This is called a double merles (or double-dapples). What most don’t know, is that a double merle doesn’t look like a merle. They usually have a lot of white on their coat or can be almost pure white. The fully pigmented splotches are much smaller and the background color is much whiter.
Is it possible to breed a Merle to a Merle. The long answer is Yes. IF you know what you are doing and do it correctly. the combination of Ma/Ma can not delete pigment to white so no risk of hearing or vision impairments. There is No deletion of pigment from Ma/Ma But a Possible pigment deletion with Ma+/Ma+.
Most Breeders practice the NO breeding merle to merle. This is the safest route for most breeders who do not fully understand all there is to the merle genetics.
Breeding a merle to merle if to done with the incorrect dogs who carry certain merle alleles can result in the dog having hearing loss in one or both ears. Having even a single M allele actually increases the chance of being deaf. However, the chance of an Mm merle (one parent is a merle and the other one is non merle) being bilaterally deaf is still less than 1%. The presence of two M genes, however, significantly increases the chance of deafness in the dog. Double-merle dogs also often have microphthalmia. This is a condition in which the eyes are abnormally small (sometimes even being barely there) and often nonfunctional. Essentially they are blind. They may also have abnormal pupils. It isn’t fully understood why this happens with the merle gene. Scientists believe that it's possibly due to the fact that the merle mutation affects melanocytes, the cells that produce melanin pigment. Melanocytes are found not only in the skin but in the eye and inner ear. They are also found in the bones and heart.which combinations of two Merle alleles can delete pigment to white and therefore come with the risk of hearing and/or vision impairments? Out of the 28 possible Merle allele combinations there are 14 that have the ability to delete pigment to white. This means that 14 combinations of the merle alleles from mating a merle to merl can result in a double merle with significant health issues.
Mc+/Ma+, Ma/Ma+, Ma+/Ma+
Mc+/M, Ma/M, Ma+/M, M/M,
m/Mh, Mc/Mh, Mc+/Mh, Ma/Mh, Ma+/Mh, M/Mh, Mh/Mh
Note - the Mh allele can delete pigment even as heterozygous.
