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The Orgins of the Merle
The information below was borrowed from Inka Cibulková, November 27, 2018
ORIGIN OF MERLE YORKIES
The classic Yorkshire terrier, today a widespread and numerous breed, was formed by combining breeds such as sky terrier, maltezacek and dandie dinmont terrier and several other breeds that are no longer present. In 1886 he was enrolled in a herd book called Yorksire Terrier just because he was bred in the city of Yorkshire. However, its appearance and character varied considerably from its present form, so its use was gradually changed from hunting dog to today's pet.
History and standard yorkshire terrier: https://www.psi-plemena.com/yorksirsky-terier-jorksirsky-t
In the same way, other breeds were born, of course, and their coloring, resulting from further and further breeding, gradually increased. It's always just a matter of time when different color variants are recognized as purebred, and that is when the offspring are nice, of a type and have all the requirements for the appearance of a given breed.
This is the reason why people do not have just black French bulldogs, beige mopes, golden labradors, black dobromany and others and more ... If I do not name breeds of different breeds such as Havana dog from poodle, etc. In short if you do not at home wolf, each breed is bred by crossbreeding other breeds and then long years of sacrificing time and money before the atypical dogs become pure, a type of dog corresponding to the description and qualities of a particular breed.
The first Yorkshire terrier in merle was born on February 17, 2011 in the kennel "von Perstadt" thanks to a breeder named Inka Cibulková .
The Merle gene (or, in other words, the gene responsible for this color) was managed by a team of scientists led by Leigh Ann Clark in 2006 (Clark et al., 2006, PNAS 103 (5): 1376-81). It was a breakthrough that finally made it possible to test dog populations also from this point of view. They have proven that SILV (Silver-locus, Pmel17) has been the gene for some time. This gene belongs to the genes known to dilute the color of the hair and its expression manifests exclusively in the area of the skin and the eyes. Genetic changes (mutations) in the SILV gene region have been found to affect the normal function of this gene, resulting in a hair pattern with areas and spots of the diluted pigment mixed with the normal undiluted pigment. The unmodified version of the SILV gene is called m, while the modified versions are called M (ie the merle gene). Changes (modifications) of the SILV gene are caused by the insertion of a mobile gene element, called the retrotransposon, which may, as it turns out, vary in length. It seems that the length of this inserted sequence also has an effect on how the modification is reflected in the dog's phenotype.
Typical M genes are expressed by known merle / leopard stains in dogs that are heterozygotes (mM) and a typical double merle with a predominant white homozygous (MM) phenotype. The second modification, described in the original article, includes a shorter version of the insertion of approximately 220-225 bp. This modification is not visible in the color of the coat, so it was termed "hidden merle" (cryptic, phantom) and is called Mc. Heterozygous and homozygous individuals (i.e., mMc, and possibly also McMc) appear to be single-colored / solid as well as homozygous individuals with unmodified gene (mm) in their genetic equipment. They can be distinguished only by genetic tests.
The "leopard" merle gene has demonstrated recent more thorough merle gene testing in the LC population. Other modifications of SILV have been detected gene, inserts of 243-249 bp, which have not yet been demonstrated in other breeds. To simplify and differentiate from both of the above mentioned types, I use the working name Ma. The length of the inserted sequence in the SILV gene is something between the normal MaMc and the phenotype is less pronounced than M, but more than Mc. Heterozygotes Ma (ie, mMa) are born as full-color / solid, but it seems that with the growing age of a dog, the merle pattern in the fur becomes more pronounced and noticeable. Homozygotes, ie MaMa, usually have a merle pattern, but all in diluted colors, that is, especially blue and probably other diluted colors, but are not predominantly white. The combination of Ma and normal M, ie MaM, gives a phenotype called patchwork where larger areas of different colors with leopard pattern and white areas are alternating. The McMa Heterozygotes also look more like one-color.
The presence of specific modifications of the SILV gene, ie Ma, explains the cases when descendants of leopard colors and patterns are born from solid colored parents. Based on previous findings, the presence of Mc without genetic analysis can not be distinguished by the phenotype.
At this point, and in our current knowledge, it does appear that no other unknown genes are needed to explain the different behavior of the merle gene. However, regulation, modification and interaction with other genes can not be completely ruled out until more information is known about the mechanisms of expression of this modified gene, the inheritance of different SINE lengths and the possible presence and effects of other genes. It can also play a role such as piebald gene, which can increase the amount of white coat color.
Determination of the merle gene is carried out by Biofocus in Germany. The methodology is based on analysis of PCR products according to specific primers. For analysis, it is necessary to isolate DNA from the starting material. Practice shows that a smaller amount of blood is a more reliable starting material.
Louisiana Catahoula (LC), with the same color, is proud. The combination of parents with merle / leopard by coloring is therefore purposeful and even the appearance of some typical defects associated with the presence of merle gene that causes this coloration, most LC breeders in the country of origin, the USA, do not deter. It is no wonder, therefore, that most of the LC population has this gene in their genetics, and that monochromatic / full color / solid individuals that are not its carriers are in this case a minority. However, this breed does not appear to have suffered much from this condition and the incidence of defects was higher than in other merle gene breeds.
The results so far confirm that LC is a "promotor" breed of merle gene. It has been shown that more than 80% of the tested individuals have been carriers of some form of merle gene. Of these, more than 30% double merle of some type and more than 30% looked solid.
Written by RNDr. Helena Synková
Merle dog coloring
The coloring of merle in dogs hides some health hazards that every breeder should know. The merle x merle must not be matched, nor does the merle gene x merle gene. For this reason buy puppies in merle color or merle gene only with a certificate of origin and only from a credible breeder! The Merle gene was mapped to dog chromosome 10 (CFA 10). This coloration of the hair is characterized by the presence of stains of the diluted basic color in areas with full pigmentation - there are irregular gray and / or beige spots on the base color (eg black, brown, red or even light). Unlike other types of hair coloration, merle brightened sites are distributed unevenly across the body.
Merle coloring occurs in a number of dog breeds, some of which are recognized by the FCI standard.
The Merle gene has two alleles:
M - merle allele causing merle hair coloration - dominant
m - allele full of hair pigmentation - recessive
A person with a full pigmentation throughout the body is always homozygous with the genotype mm .
The Merle individual can either be homozygous with a MM genotype or a Mm genotype.
Hidden Merle and Cryptic Merle
Hidden merle are merle pesi (mM), which can not detect marbled hair (it is not commonly known for red, gold, or cream or cream color).
Cryptic merle are individuals with very low merle coloration and as a result are sometimes mistakenly considered to be non-merle individuals. The lack of visible merle coloration may be the result of a reduction in the amount of merle, or it can only be hidden under white characters. For example, a puppy looking like a black tricolor male, having a merle-colored tail only, was described. Or merle can only be colored on the edge of one ear, one elbow, one on the thigh ...
All of the non-merle puppies must be thoroughly inspected if they have no less spotted merle stains. If such a stain is found, it is not a merle, but a blue / red merle, referred to as called cryptic / hidden merle, especially in the long coat, the small area of merle can be extinct and such a person will be guided as a non-merle in the pedigree, and later can be contacted with another cryptic / hidden merle by the breeder so surprisingly the merle-colored puppies , which may have different health problems due to an inappropriate combination of parents. Health complications that are related to the merle allele or what problems does an inappropriate connection cause:
As with white coloring dogs, signs of "albinism" such as hearing and vision abnormalities, including mild to complete deafness, increased intraocular pressure, ametropia (poor refraction ability), colibos, may occur due to inappropriate pairing of merle homozygotes. Individuals with genotype MM (double merle) may also be associated with skeletal, cardiac and reproductive system abnormalities.
These dogs often have heterochromia iridis (corneal variation), often with blue eyes, or only one blue eye. Individuals with merle staining have a visibly little pigment on their eyes, which can affect their visual abilities.
Hearing anomalies also occur in the merle of individuals due to the absence of pigment in the hairs in the ear canal. Sound waves can not spread (longitudinal oscillation of air molecules) into the middle and then inner ear of the individual, resulting in partial to complete deafness. Homozygous merle (MM) are very pale, sometimes whitish, the color of their mucous membranes is also lightened to pinkish and pigmentation of the eyes mostly blue ALBINISM .
