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I have a few questions about breeding and color genetics in dogs. I've always raised horses so dogs are a new thing for me. I've always owned dogs, just never bred them.

I've been looking at different coat colors and was wondering if dog's were like horses as far as genetics go? For instance, an Australian shepherd with the merle coat has a dominant gene. But then say you breed it to a different breed of dog that is solid, like the poodle, and in that breed the solid color is the dominant gene. Are the puppies 50/50 chance or merle or solid?? (I'm not breeding any dogs just a curious color question because I've been looking at a lot of aussiedoodles)
 

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I recommend this page if you want to learn of dog color genetics:

http://www.doggenetics.co.uk/

The color of a dog is determined by a number of loci. Some colors can mask some and reveal others. The coat has two pigments: yellowish or red phaeomelanine and black eumelanine. Their distribution in the coat determine the appearance. White is absence of pigment.

Merle and solid colors are in different loci and do not cancel each other. Merle pattern is only visible on eumelanine so it is difficult to see on a dog that is mostly or only yellow (sable or ee). There are already dogs that are solid black with merle like bi-merle Shelties, bi-merle border collies and Aussies, and a breed without white markings, the Mudi (a Hungarian herding breed).
So, let's cross a merle Aussie and a black poodle. Your litter should be half merle, half not merle (M locus). Most likely all solid because of the poodle (K locus). If both parents carry chocolate, some of the puppies can be chocolate or chocolate merle (B locus). Some breeds like Aussies call this red. If the poodle isn't KbKb but Kbkbr or Kbky and the Aussie isn't bi-merle (black and white with merle) you can have puppies that show A locus pattern, most likely tan point, with or without brindling depending on which allele the poodle carries (in order of dominance: Kb dominant black, kbr brindle, ky not black not brindle).
 

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I continue about merle. Two merle dogs should not be bred together because if a puppy inherits the merle allele from both parents it will be so called double merle. Double merle is not lethal but will produce deformed puppies that can be deaf and blind. If you are breeding merles with a risk of dogs with no or little eumelanine in its coat you should DNA color test the parent or puppies who don't have enough eumelanine to determine whether the dog is merle or not to keep from breeding a merle to merle later on.

To make it more complicated, the mutation that causes merle is a string of duplicated base pairs that can have different lengths. So you have different types of merle and they also look different. The merles that have the short version should be safe to breed together or to normal merles. Not all labs can test different merle lengths yet.

When I look at a dog, I assess its color like layers in this order

E locus - Em, E, e*, e - eumelanine mask (visible on sable and tanpoint), non-masked, a group of domino alleles, recessive yellow - this locus can mask other loci because its most recessive allele e removes all eumelanine from the coat leaving only phaeomelanine.
K locus - Kb, kbr, ky - this locus determines if the dog is solid black (or brown blue or lilac), brindle, or showing A locus without brindle.
A locus - Ay, aw, at, a - sable (brindle if kbr-), agouti (wolf), tan point (brindle point if kbr-), recessive black - the pattern of this locus is visible if the dog is not ee or Kb. Brindle affects the yellow parts.
B and D - B, b and D, d - brown (bbD-), blue (B-dd), and lilac (bbdd) - turns all eumelanine into brown (chocolate, liver), blue or lilac. Does not affect phaeomelanine. On an ee yellow, look at the nose lips and eye rims.
M locus - M, m - merle, not merle - makes eumelanine to have lighter areas. Causes blue eyes. Does not affect phaeomelanine.
White spotting - solid, Irish spotting, piepald, panda, white head factor - it seems all these are in separate loci. Head white and panda are dominant IIRC, other spotting recessive. Other genes do not mask these except you cannot see white markings on a very pale ee dog.
T locus - T, t - ticked, non-ticked - only visible on white spotting, causes little dots in base color appear in white markings when the puppy grows. Density varies. Also called roan.
Saddle and creeping tan - I know saddle is dominant, it affects tan point and agouti
G - early graying in bearded dogs. Dominant. Not visible on smooth-coated dogs.
Unknown factors affecting phaeomelanine intensity and causing urajiro
Breed typical color patterns like Great Dane harlequin (dominant, lethal as homozygous, visible only on merle), husky blue eyes, and Dalmatian spotting that turns ticking into coin-sized spots.
 

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I recently did a DNA test on my dog for breed and one of the things it also tells you is coat and skin pigment. I found it pretty interesting as a horse person who has also had a mild interest in horse color genetics.

So my dog genetically is brown or yellow and he has one gene for pigment that makes his lips nose and paw pads black even though his skin is pink. He also has a double gene for white spotting.

Visually He is al all white dog with apricot colored ears, black lips and paw pads and pink skin.
 

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My Golden Doodle is from a purebred Golden Retreiver by a merle and white Poodle. He had a little Australian Shepherd far back in him. The Golden Retreiver mother had several merle colored pups along with the usual shades of Golden.

Bonnie is merle colored. I bred her to a cream colored Poodle twice before I got her spayed and both times she had one merle colored pup. The other pups were black or golden.
 

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Some of the golden puppies can be genetically merles because the merle doesn't show on hair that has no black.
 
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