Dachshund Double Dapple

Breeding dapple to dapple can produce Double Dapples and they can have very serious genetic issues that can cause puppies to be born without eyes, deafness and other body abnormalities. Double Dapples are not accepted by the Kennel Club UK or USA Clubs. Quite a few Breeders in the U.S.A do breed DOUBLE DAPPLES. Currently in the UK this doesn't happen with responsible KC breeders. The reason breeders risk trying to breed a Double Dapple is that they will eventually get a normal perfectly healthy dog and that dog will look truly stunning (see picture below) with additional white patches over the normal single dapple. Double dapples can be bred by mating two dapples - the pups from that mating will be normal colours, single dapple and double dapple. If two double dapples are bred together then all the pups will be double dapples. From time to time red and cream dapples loose their dapple over time and are mistakenly then taken for shaded reds, creams and thus bred with single dapples, so it is important to try not (unless you fully understand the risks and implications) to breed single dapples with reds or creams just in case these dogs have lost their dapple colouring.

Double dapples can be indentified by patches of WHITE in addition to normal dapple markings.

More information and pictures can be found HERE

The big PLUS? of a double dapple is it will always produce all dapple litters NO MATTER WHAT COLOUR THE OTHER DOG IS so essentially this issue is more about disreputable breeders being greedy given dapples normally fetch more money than base colours and those who are prepared to maim a few dogs for the sake of pretty colours. We do not breed double dapples not would we encourage anyone else to do so.

Double Dapple	Dapple	Black/Chocolate and Tan	SAFE?	Pups from Breeding - Note % is a guide prediction and may or may not be correct!
	X X As of 1st January 2010 no dapple to dapple matings will be allowed to register pups with the KC		NO	25% Base colour, 50% Single dapple, and the issue in this equation 25% Double dapple which may or may not have health issues but more likely than not. This mating could of course have no doubles in it but the possibility is there so you shouldn't do it.
XX As of 1st January 2010 no dapple to dapple matings will be allowed to register pups with the KC			NO	1100% double dapples which may or may not have health issues but more likely than not.
X		X	SAFE	1100% single dapple
	X	X	SAFE	50% Base colour, 50% Single dapple
Double Dapple	Dapple	Red/Cream	SAFE?	Pups from Breeding - Note % is a guide prediction and may or may not be correct!
	X	X	MEDIUM	50% Base colour, 50% Single dapple - This mating contains the risk that pups may go unidentified as dapples and thus cause a dapple to dapple mating at a later point in time. It is our personal recommendation that the ONLY SAFE OPTION with pups from such a litter is that from a breeding point of view they should always be regarded as dapples even though they don't show visible signs of being dapples - see Phantom Merle. When the merl dna test finally becomes available we would recommend any pups that DON'T look like a dapple from a litter containing a dapple parent be tested regardless of appearance. At that point should they test negative they may safely be regarded as non dapples.

Long technical version

Dapple is the name used with Dachshunds but is the same as Merl used in other breeds. Canine coat colour is determined by the expression of a specific combination of genes. A gene, the basic unit of heredity, is comprised of a unique sequence of DNA and directs the production of a specific protein. Proteins are required for the structure, function and regulation of the body’s cells, tissues, and organs. Genes are located within chromosomes. Dogs have two sets of 39 chromosomes in every cell, one set inherited from each parent. The location of each gene within a chromosome is referred to as its locus. While there is more than 99% DNA sequence similarity between dogs, variations in DNA sequence do occur in a small number of genes. Different forms of the same gene are called alleles. Dogs can have two identical or two different alleles for a particular gene. If both alleles are identical, then the dog is said to be homozygous at that gene; if both alleles are different, then the dog is said to be heterozygous at that gene. The genotype of an animal is its genetic identity, as identified by the alleles it carries; while the phenotype, or appearance, is the expression of those alleles. Coat colour in dogs is usually controlled by a set of genes. These include the colour genes, genes that affect the pigment colour of hairs, and the pattern genes, those that affect the distribution of a particular colour. At least 20 genes have been identified that affect coat colour in dogs.

Merle-Dapple Coat Colour Patterning

The merle coat colour is characterized by patches of dilute pigment in combination with areas of full pigmentation. Therefore, the merle gene acts to lighten whatever coat colour would otherwise be expressed. However, unlike other dilution genes, the lightening effect is not spread evenly over the coat, but is expressed as patches of diluted colour scattered over the dog’s body. If the basic colour of the dog is black, the effect of the merle gene is a soft gray, often referred to as “blue”. If the basic colour of the dog is red, the effect of the merle gene is a pale red. The merle coat pattern is characteristic of a number of breeds including the Shetland Sheepdog, Collie, Border Collie, Dachshund, Australian Shepherd, Cardigan Welsh Corgi, and Pomeranian.

Genetic Inheritance of the Merle-Dapple Gene

The merle gene (M) is inherited in an autosomal fashion. In other words, the trait is not linked to gender and can be passed on from either the mother or the father. The gene is incompletely dominant, or a gene that has intermediate expression. A heterozygous dog, carrying only one copy of the merle gene (Mm), expresses the characteristic diluted coat colour pattern. A non-merle dog (mm) is normal in colour, while a homozygous double-merle (MM) is predominantly white. Punnett squares can be used to determine the expected coat colour of offspring when breeding dogs of known genotype (i.e. coat colour genes have been identified). In the example illustrated, a non-merle dog (mm), indicated in the vertical column, bred to a heterozygous merle (Mm), indicated in the horizontal column, will give rise to offspring with an expected frequency of 50% merle (Mm) and 50% non-merle (mm). Dogs that carry the merle gene but do not show the characteristic merle phenotype, are known as cryptic merles. These dogs may give rise to merle offspring. It is suspected that the DNA sequence of the merle allele in the cryptic is shorter than the allele expressed in the typical merle dog. The harlequin coat colour pattern in Great Danes is produced through the interaction of the merle locus and the harlequin (H) gene. In harlequin Danes, the merle background colour is diluted to nearly white with fully pigmented black patches.

Health Problems Associated with the Merle-Dapple Allele

You should never breed two heterozygous merle (Mm) dogs together because it produces the homozygous double merle (MM). Homozygous double merle (MM) dogs may exhibit auditory and ophthalmic abnormalities including mild to severe deafness, increased intraocular pressure, ametropia, microphthalmia and colobomas. The double merle genotype may also be associated with abnormalities of skeletal, cardiac and reproductive systems.

Ametropia: vision impairment due to a refractive error such that images fail to focus upon the retina.
Microphthalmia: a smaller than normal eye due to a defect occurring early in development. Affected dogs may have prominent third eyelids. Other eye defects are common in animals with this condition, including defects of the cornea, anterior chamber, lens and retina.
Coloboma: a defect in ocular tissue; a cleft or missing portion of components of the eye, most commonly affecting the iris.

Phantom merles

Merles that do not have the merle phenotype (appearance) may still have the merle genotype (Mm). These merles are called phantom merles or cryptic merles. Phantom merles should never be bred because they may produce phantom merle offspring. Phantom merles may accidentally be bred to other merles (Mm) which would produce devastating (MM) merles with the health problems described above.

Other websites with Dapple information

Dachshund Breed Council Dapple information sheet - please click here