merle coloring in dogs and associated deaf/blindness (autism posting)

alright, let's start with a quick definition

“also know as dapple, merle is characterized by irregular blotches of fur set on a lighter background of the same pigment, such as solid black on gray (called blue merle) or solid brown on tan (red merle).” -American Kennel Club

Merle is a dominant color gene meaning it (almost) always presents itself phenotypically when apart of the dogs genotype even when it is a heterozygous gene. merle is a very popular and desirable color and because of this is often sold by breeders for a higher price, though an ethical breeder shouldn't be charging more for a certain color.

if a merle (Mm) and a non merle (mm) are bred together there is a 50% chance each pup will be merle. if you breed two merle's (Mm) together that chance raises to 75% but, you run the risk of producing a double merle (MM) which have a heightened chance of health issues

The most common health risk with merle dogs is deafness, even single merles (Mm) have an increased likelihood of these issues. Double merles (MM) are at a even higher risk for deafness, one study finding 85% of MM dogs were bilaterally deaf.

On top of the deafness MM dogs often have very small and often non-functional eyes (microphthalmia).

double merle's can occur for a few different reasons

1. in feral/stray populations dogs will be breeding and obviously they don't understand that how genetics works so two merle's can mate producing a double merle. though it's unlikely and deaf and blind dog will survive long without human intervention

2. similar to option one is ignorance on the owners part! it may be an uneducated breeder or an oops-litter but an owner who doesn't understand or know about the dangers of double merle's make accidentally creat one.

3. greed! though many double merle's are born infertile if you were to get a double merle bitch (MM) who is able to produce pups and bred her to a regular sire (mm) you would have a litter of all single merle puppies (Mm) which as previously mentioned can be sold for more.

over all, merle dogs are very pretty but you should be aware of the risks this coloring can have especially in double merle's.

thank you for coming to my autism rant, have a good day