Coat Color Inheritance in Beagles
Probably the most definitive book on coat color inheritance in all breeds was written many years ago by Clarence C. Litle in his Inheritance of Coat Color in Dogs (Howell Book House, New York, 1957). While it may be that new evidence has come to light regarding coat color inheritance in general, no new book has ever replaced this one, and this is what we use for the basis of this page.
Short lesson in genetics: In genetics we have what is called Phenotype, or how the dog looks, physically, and Genotype, which the genetic makeup of the dog, which may or may not be totally expressed in the phenotype. In addition, there are genes which are more dominant than other and are thus called Dominant (which are represented in charts with a Capital letter) and others which are not as strong in expression which are called Recessive (which are represented in charts with a Lowercase letter). Each dog receives one set of genes from each parent. It is the combination of these many genes which are responsible for not only his coat color but how long his ears are, how dark his eyes are and the shape and his entire conformation and quite often his health prospects.
In any set of genes there are also what is called Loci, locations on the chromosomes, which may only be occupied by two alleles or genes. However, there may be more than one set of alleles governing some aspects of coat color such as degree of white, depth of brown coloration and the amount of black. Such genes are called modifiers. It is not necessary to get into a deep discussion of how modifiers work or the discussion of incomplete penetrance and such. If you want to know more about this, there are many good books on genetics.
For the Beagle, these are the following Loci involved:
Locus A: Allows or restricts formation of dark (black or brown) pigment, As, which allows for distribution of dark pigment over the whole body (one color only). Very rare in beagles. ay: Restricts dark pigment greatly, and in its most complete expression produces a clear sable or tan dog, such as the red and white basenji. Doubtful in beagles. at: Produces tan "points" such as the typical tricolor, black and tan or liver and tan. All beagles are homozygous (pure, with both alleles being the same) for this condition regardless of their color, even lemon and white. aw : This is the "wild" or agouti color which allows for a banded type of hair. In beagles this seems to be restricted to certain areas such as along the neck, and sometimes the back and whithers.
Locus B: Determines if dark pigment formed at the A Locus will be black or brown, which includes liver and chocolate). Tri-colored beagles are Bb (heterozygous) or BB (homozygous, dominant). Liver or chocolate bealges are bb (homozygous, recessive).
Locus C: Allows for rich pigmentation, resulting in dark tan or red areas and absolute black or liver areas. cch: Called the Chincilla gene, this reduces the richness of pigmentation, but usually its effect is only visable on red, tan or yellow pigmented areas, and which may become lighter in shade towards lemon, buff or cream.
Locus D: Determines the dilution factor for dark pigment. D: Causes black or brown to remain black or brown. d: Dilutes black to so-called "Maltese" blue (actually a gray), and brown to silvery, as in the Weimaraner. The dog must be dd (homozygous, recessive) to be "blue" with both parents contributing the d gene for the color to appear.
Locus E: This determines the extension factor for dark pigment. E: Allows dark pigment (black, brown or their diluted forms) to extend throughout the areas where produced. e: Prevents extension of dark pigment, leaving the animal a clear red, tan or yellow in non-white areas. The dog must be ee (homozygous, recessive) to be lemon or red and white. Ee or EE would produce a tri-color. This is why in beagles the "red" gene is recessive to the tri-color gene, which is actually a recessive to the red in other breeds, such as Basset Hounds.
Locus M: A dominant Merle (M) factor seen in collies, dachshunds, Cardigan Welsh Corgis and some other breeds. Not observed in beagles, therefore beagles possess the genotype mm.
Locus S: The spotting factor. S: Causes pigmentation of the entire surface -- no white, except possibly an isolated spot, as on the chest. Rare in beagles. si: Irish Spotting, (white feet, legs and chest) and blaze. sp: Piebald Spotting. Colored head and blanket with the rest of the surface white. sw: Extreme white piebald spotting where the dog is almost entirely white, except for dark patches at the eye, ear or near the base of the tail. Because of the wide range of "spotting" it is often difficult to determine between the sp and the sw genotype.
Locus T: The ticking factor T: Allows ticking of the dog's dark pigment color to appear in white areas. t: Absence of ticks in the white area.
Here then, are the genotypes for the more common colors of Beagles:
atat B? C? D? E? mm sP? tt: Tricolor (Black blanket, tan points, no ticking). A dog with ticking, you would substitute Tt or TT for the tt.
atat bb C? D? E? mm sP? tt: Tricolor (Liver blanket, tan points, no ticking)
atat B? C? dd E? mm sP? tt: Tricolor (Blue blanket, dull yellow points)
atat B? C? D? ee mm sP? tt: red and white (white dog with varying degrees of tan or red patches) Cch would give a rich pigment or "red", but could throw pups which would have the tan reduced to buff.
atat B? chch ee mm sP: Lemon and white (white dog with lemon or buff patches)
atat B? C? dd ee mm sP?: Red, white and blue, more properly termed a blue-factored tan and white, which would look like a lemon and white dog but with dull buff points, light nose and eye pigment)