(Two articles are reproduced here

MANTLEDANE GENETICS: How to Get and Keep Boston-patterned Dogs

And

PHENOTYPE IS NOT GENOTYPE: Or Why The Irish Gene Is Not The Mantle Gene

(Two Separate Articles)

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MANTLEDANE GENETICS: How to get and keep Boston-patterned dogs

As the "6th class" has now been approved by the GDCA, and mantle danes will soon grace the conformation ring in the U.S.A., a discussion of the genetics involved in acquiring and maintaining the pattern Harlequin breeders have traditionally referred to as the "Boston" would seem in order. Although approval of what exactly constitutes the correct markings for the mantle Dane has yet to be fully articulated and approved, Harl breeders have a general idea of what describes the boston-patterned Dane. This description ideally refers to a black and white dog with a coat, or mantle, of black that extends over the topline from the withers to the croup, with four white stockings, a full white collar, white belly and tail tip, and generally a white blaze on the head--with black fully covering both eyes and both ears. This pattern is seen in a variety of other breeds besides the Great Dane, and many base colors (e.g. fawn, brindle, blue) can coexist with this pattern. The pattern is a result of the action of genes (alleles) present at the so called "recessive white" or "spotting" series (S Locus). In dogs, this series has four basic variations (alleles) that produce a range from a solid or "self-colored" dog through varying amounts of white spotting to an all white dog (see illustration). Each of the four genes (alleles) in this series produces a range of white on the dog rather than a specific amount of white. And, although the first lesson of genetics revolves around Mendel's Laws, which state that genes sort independently, acting more like different colored marbles combining in dominant recessive pairs, than like paints mixing on a palette, there are exceptions, and the recessive white series is one of them. This gene demonstrates incomplete dominance, so that the "painterly effect" does occur when two genes combine. The classis example of incomplete dominance in genetics is the four-o'clock flower, in which cross-breeding two true breeding (homozygotic) red and white strains does result in pink flowers, rather than the expected dominant red flowers in the first generation, with the recessive white showing up in the second generation.

The recessive white series (S Locus) is further complicated by modifier genes which act on the main gene to increase or decrease the amount of white present in individual dogs. The main gene only allows a certain amount of variation in the amount of white; however the modifiers' effect results in both individual dogs with the same main gene having a somewhat different appearance, as well as an overlap in the appearance of dogs carrying different combinations of genes of the four main genes (alleles) in the recessive white gene series. For example, dogs who carry only the solid or "self" gene of the recessive white series can vary, due to the actions of modifiers, from completely colored to having white on the feet, chest and/or belly. Fawn, brindle, blue and black Danes typically have this pattern and carry only "self" genes. When breeding these dogs, if white is present at all it will be confined to these specific areas; you won't see dogs with blazes and collars, but you cannot always get a completely colored dog every time, due to the action of modifiers.

The next gene in this series produces a range from what Dane breeders refer to as a "mismarked black" to a full collared boston at its extreme range. Many breeds carry two of these genes (alleles) commonly; typical examples are seen in Collies, Basenjis and Boxers. In these breeds, generally no more than 1/3 white is allowed, and this 1/3 white represents the most white this gene (allele) can produce with a full extension of modifiers. These breeds typically allow less white to be present, and this reflects the general action of this gene, which produces white feet, belly/chest and/or throat commonly, with or without a broken (partial) or full white collar. Again, you can breed for the general pattern of "no more than 1/3 white," but it is unlikely that all individual dogs will carry the correct modifiers to produce only offspring who hve the full extension of white that results in a full collar. This gene is referred to as the "Irish" gene (allele), and generally produces a more symmetrical pattern than the piebald gene described below. There is some dispute over whether this Irish gene is present in the Great Dane: the patterns commonly produced by this gene can also be produced by the piebald gene or the combination of the piebald and solid genes.

The next gene in this series is referred to as the piebald gene. This is the gene traditionally believed to be commonly carried by the majority of Harlequins. This gene is also seen in spaniels, pointers and Beagles, and it produces a range of white from partial collared dogs through a variety of spotting patterns to dogs predominately white with only head and tail-root color. Breeds which focus on this gene describe the pattern generally as parti-colored or simply piebald, and do not specify the exact amount or location of white required. Modifiers alter just how much white each dog will have and therefore there will be varying amounts of white in the offspring of piebald dogs. For Harl breeders this range includes "mismarked" blacks and bostons all the way to "boston/merle/harl-heads," in which the dog lacks all body color. The main gene itself, without the extreme action of modifiers, would theoretically produce a dog Harl breeders would recognize as a boston, but restriction of modifiers leads to a "mismark," while extension of modifiers leads to a dog predominantly white. The last gene in this series is referred to as "extreme-white piebald." These dogs are commonly white, with any color present being confined to the head and/or tail root. Sealyham Terriers, Bichon Frise, and Pyrenese carry this gene and display the typical pattern this gene produces. This is the gene that produces the white Boxer and the (non-merle) white Collie that is occasionally seen. It is possible that this gene is carried in the Harlequin family of Danes, and if so, it may be responsible for some of the dogs born who lack body color.

As you can see, there is an overlap in the ranges of white produced by these varying genes in the recessive white series: the solid gene with full extension of modifiers overlaps the Irish and piebald genes with full restriction of modifiers. The piebald gene overlaps the entire series of the Irish gene and is only typically distinguishable as producing generally more white in the offspring with less symmetry of pattern. The piebald gene, at full extension, also overlaps the extreme-white piebald at full restriction (see illustration). There are therefore, several different ways to get the mantle Dane pattern (i.e. different genotypes that produce one phenotype). A mantle Dane could be a "pseudo-Irish" mantle, carrying one self and one piebald or extreme piebald gene which combine to give a full collar. A mantle Dane could carry two piebald genes wth restriction modifiers. A mantle Dane could carry two Irish genes with full extention of modifiers (assuming this gene is present in the Great Dane). A mantle Dane could also result from the combination of one Irish and one piebald or extreme piebald (assuming the latter is carried by the breed). Of these six (6) possible genetic types (genotypes) of mantle Dane, only two are pure breeding (homozygotes), while the other four are hybrids (heterozygotes). When it is possible breeders naturally prefer pure-breeding dogs to hybrids to be able to consistently fix a certain type, in this case a certain pattern, through several generations. Of course, it has already been noted, that when dealing with the recessive white series, an exact amount of white cannot be predicted; control can only be achieved within a range of a specific gene in the series. Although all these dogs would basically look alike (i.e. meet the mantle Dane standard), their underlying genetics are different and will result in varying percentages of acceptably marked offspring and distinct types of mismarked offspring. The clues to which "genetic kind" of mantle Dane an individual dog is can be found by studying its pedigree and knowing the color patterns of its siblings. This underlying "boston" pattern, of course, affects where the patches will be on Harlequin offspring as well. For example, an underlying full collared boston pattern will ensure the "pure white neck preferred" by the standard. An underlying pattern that is "mismark black" will allow patches to form on the neck of Harlequin offspring. An underlying pattern in which modifiers do not allow body color to form will result in (disqualifying) "harl-headed dogs; Harlequins without any body patches.

If a dog is a pseudo-Irish boston (Ss), he will most likely have solid colored Danes clearly in his pedigree. His siblings were likely very close to solid, or appeared as ("flashy") piebalds and bostons. His offspring will generally have the same split: a few near solid pups and the rest with flashy markings. It is possible in the first generation to get full-collared bostons breeding undermarked (harl-head) to overmarked (mismark black) dogs by making a king of (Ss) pseudo-Irish type of boston, however the under and over marked animals will reappear in the succeeding generations, increasing the number of disqualifying mismarks in the litter. In the other types (ss) of hybrid bostons, there will be few, if any, near-black animals in the pedigree and among the siblings. The offspring of these hybrids will tend to have a lot of white on them (when bred to one another), with "true" piebald, predominately white and near-white animals occurring, as well as some boston patterned dogs present. If such is bred to a pseudo-Irish boston, the offspring in the first generation will appear like the pseudo-Irish (i.e. boston), but more and more white will show up in succeeding generations, as the recessive white patterns recombine. Most of the offspring of all these breedings will also be hybrids; the occasional true-breeding solid (SS) may be obvious, but any true-breeding Irish and/or piebald bostons may look very similar to their hybrid siblings.

A true-breeding piebald boston has two genes for piebald and modifiers that restrict the amount of white present. This dog will have a pedigree of black and white dogs with distinct white markings. There will likely be a wide variation in the white markings, both in amount and location. There are probably individuals present in the pedigree with distinctly asymmetrical markings. The offspring of piebald boston matings will show the same pattern; no individual dog will be without distinct white markings and there will likely be a wide range of how much and where the markings occur. Piebald to pseudo-Irish boston will produce offspring that can range from near black to near white. Piebald boston bred to the other hybrids will produce distinctly black and white animals, and near white animals will occur occasionally. (Of course these offspring of hybrids will also generally be hybrids themselves.) A true-breeding Irish boston has two genes for the Irish pattern and modifiers that extend the amount of white present. This dog will have a pedigree with "mismark" and near-black dogs, with no more than the 1/3 white that is typical of the Irish pattern. There should be a distinct symmetry to the white markings present. The offspring of Irish bostons will show the same pattern, with no pups having more white than is found in the ideal boston, and most pups having less than a full collar (with some totally lacking a collar). Irish bred to pseudo-Irish boston will produce very similarly to an Irish breeding, however there may be occasional pup who is much more white or more black than his parents and all the resulting pups will be hybrids and carrying for more white than shown on their parents. Irish bred to piebald boston will also produce Irish patterned hybrid offspring, with likely more white than the Irish parent shows.

To produce full collared Mantles and Harlequins with the preferred white neck consistently through several succeeding generations, it would be wise to breed only from correctly marked specimens (i.e. show marked dogs). Breeding other "off-color" patterns may result in the introduction of hybrids, modifiers and recessive genes difficult to control in succeeding generations. As there are several different genetic possibilities for what is described as a boston, the underlying genes involved are currently difficult to determine. However offspring who receive the boston pattern are the best candidates for a future breeding program. Breeding animals with disqualifying faults, such as "mismarked blacks" and "boston-heads" may very well combine in the first generation to produce some animals with the boston pattern, but these animals will be hybrids from mismarks and therefore be unlikely to reproduce themselves, as the desired combination of genes will be lost in succeeding generations. There will always be a higher percentage of mismark offspring when breeding from such hybrid stock. If only full collared Mantles and Harlequins with the preferred white neck were to be used in a breeding program, it might be possible, by concentrating on acquiring pure-breeding stock, to somewhat "fix" the range of the recessive white gene in question. Certainly a breeding program for harlequin and mantle Danes needs to concentrate on breeding animals who fall within the standard. This concentration on breeding only correctly marked animals will result in the highest possible percentage of correctly marked offspring over time. Naturally all dogs used in a breeding program should conform closely to the standard of the breed in all other ways; inferior dogs having the correct pattern should not be used. The genetics involved in producing a mantle Dane may seem complex when compared to that of the solid varieties of the Great Dane, but producing correctly marked mantle Danes and avoiding dogs who produce predominantely mismarks will still be easier than that of making their Harlequin siblings; a challenge, indeed, to which any competent harl breed can attest!

*This article was first publish in the Great Dane Reporter, Mar/Apr 1997 issue. All copywrites apply.

I'd like to make the note that it would seem inescapable that some and not all Mantledanes carry some sort of allleles, be they modifiers or a more "direct" and separate locus, that contribute to the production of harls (over merles) in harlequin litters. This is implicit in much I (and others) have written , but is rarely explicitly stated, but certainly should be addressed at part of the family inheritance, as should the implication that follows directly from this observation, namely that Mantledanes, as individuals, contribute "unevenly" to the production of harls, with some unable to offer any "help" to the increase in the percentage of harls in a litter, while others might, at least under certain theories, carry strongly enough for whatever constitutes "harlequin genes" to not only increase the percentage of harls in a litter from a harl x mantle breeding, but actually produce harlequins from a merle x mantle breeding. JPY

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