Can Someone explain "Double Merle" to me?

[StillandSilent]

Ok. Our shelter just took in 2 purebred Aussie puppies. (At least is was claimed they are purebred.). Both of them are white with blue eyes and a little bit of black shading on the ears. Both of them are deaf. The person who surrendered them to animal control shrugged and said it was because the mother was a double merle and that led to some birth defects in the pups, including a blind puppy and these two.
As I understand it, a double merle comes from breeding a merle dog to a merle dog. But why does this result is birth defects? Is it similar to many white animals with blue eyes having defects, or is it something else entirely. I have looked it up on the web, but the sites I found were extremely technical and I have zero breeding experience. I am very confused and I know there are many responsible breeders here who can explain in simple terms for a layman

[jess2416]

http://www.lethalwhites.com/doublemerle.html

[StillandSilent]

Thank You!

[jess2416]

Your Welcome, I hoped it helped

[Zoom]

Jess beat me to it.

Basically it's breeding a recessive to a recessive and that causes all sorts of problems for any animal. Northern breeds seem to be exempt from the "white+blue eyes=trouble" equation.

[Melissa_W]

I really like this link as well.

Elementary Merle Genetics
http://bowlingsite.mcf.com/Genetics/Merle.html

[stevinski]

I really like this link as well.

Elementary Merle Genetics
http://bowlingsite.mcf.com/Genetics/Merle.html

thats what i was goin to advise too lol!

[Jynx]

I have an aussie out of a merle x merle breeding. He is a black bi. Two in the litter were born deaf, 4 were ok. If y ou can locate aussie rescue in your area, they are normally really helpful in taking in and placing, not only healthy aussies, but deaf ones as well.
Diane