Great Dane Breeder
If Great Dane breeders could predict canine coat color, they would be able to make breeding decisions much easier. Through techniques such as DNA testing and gene mapping, scientists are learning insightful information about coat color in dogs that challenges long-held beliefs. Even so, the genetic complexity of canine coat color is filled with surprises. Great Dane breeders can contribute to genetic research on coat color as well as other traits, Schmutz says. She attributes much of the coordination of Great Dane DNA studies currently under way to J.P. Yousha, owner of Chromadane Kennel in Texas and Chairman of the Health and Welfare Committee of the Great Dane Club of America. Yousha also helped Schmutz to understand the terms many Dane owners use when describing their dogs’ coat colors and patterns.
Great Dane Breeder Early Coat Color Genetics
Great Dane Nearly 50 years ago in 1957, Clarence Little wrote “The Inheritance of Great Dane Coat Color in Dogs.” His text, which became a classic on coat color, contains information Little obtained from breeders and from his own crossbreedings of dogs of different coat colors. Little developed several hypotheses on the number of genes and alleles that determine coat color. Little labeled the positions, or loci, of coat color on paired chromosome as: A for agouti, B for brown, C for albino, D for blue dilution, E for extension, G for graying, M for merle, R for roaning, S for white spotting, and T for ticking. Little’s work continues to provide valuable reference material to scientists today; however, new technologies are helping to enrich understanding about coat color genes.
At the University of Saskatchewan in Saskatoon, Canada, and Stanford University in California, researchers have found that Little’s E locus contains three alleles red (e), black (E) and the variant that causes masking (EM) rather than the four alleles red, black, mask and brindle that Little described. It appears that Great Danes are either E or EM and do not carry e.
The finding by Sheila Schmutz, Ph.D., professor of animal and poultry science at the University of Saskatchewan and her colleagues is significant for breeders of dogs in which masking is important, such as in brindle and fawn Great Danes. Schmutz’s group refers to Little’s E locus as the melanocortin receptor 1 gene (MC1R), named for the gene’s protein. “Our MC1R studies are a good example of how DNA studies are proving Little both right and wrong,” Schmutz says. “In a few breeds of dogs, a black mask appears to be a fixed trait, but that’s not the case with Great Danes,”
Schmutz says. “In Danes, masking is a dominant trait that, when present, is visible on dogs with fawn and brindle coats. However, the dominant mask trait also can be carried by black or blue Great Danes and harlequins and merles it’s just not noticeable in these dogs because of their dark coloring or spotting pattern.” Little’s work, which came before DNA testing, is based on hypothesized alleles at hypothesized loci to fit data obtained from coat colors and patterns of dogs from various breeds and litters, Schmutz says. “DNA research has shown that there are more genes involved than those hypothesized by Little and that the actual number of alleles at genes he discussed is more for some genes and fewer for other genes. We are far from identifying all the genes involved in dog coat color using DNA, but there seems to be many more than Little predicted.”
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For Great Dane breeders trying to determine the genes carried by dogs for upcoming litters, they should keep in mind that no gene acts in isolation. “All dogs have all these genes. In some breeds, the alleles are fixed, meaning all dogs are homozygous for the same allele,” she explains. “As a rule of thumb, the more coat colors that occur in a breed, the more genes that are needed to explain the genotype and phenotype.”
Great Dane DNA testing become available for the masking trait. Now a breeder can test her black-masked fawn to determine if she is homozygous for black mask and thereby know in advance that all the pups she will have, irrelevant of the sire chosen, will also have a black mask. Alternatively if the bitch tests heterozygous for mask, the breeder may choose to search out a sire that is homogenous for black mask. Understanding coat color genetics begins with basic biology. Inside each cell are genes, tiny biochemical structures that carry traits from one generation to the next.
Made up of deoxyribonucleic acid (DNA), genes are strung together to form long chains of DNA in chromosomes. The DNA contains the blueprint of genetic information for directing protein synthesis or production. The proteins are then used to make cells, tissues and organs. Gene expression is the process by which a cell makes a protein according to the instructions carried by a gene.
Some alleles are dominant and others are recessive. A dominant allele conceals the effect of its recessive partner, meaning the dominant allele is expressed but not the recessive allele. A trait that results from a recessive allele is evident only in an individual that has two recessive alleles for that trait. Fortunately, not all dogs are either black or blue. But the more complex the coloring, the more alleles are involved and the more possibilities for variations in the genes passed from litter to litter. In the case of the black Great Dane mated with the harlequin, the Punnett square would have to be much larger, with many more squares, as this breeding involves a much more complex situation. A Punnett Square would probably have to include at least four pairs of alleles, as the inheritance of the harlequin pattern, the merle pattern, and the fawn and black coat colors would have to be diagrammed.