Am I right in assuming that mating 2 harlequin Great Danes can result in puppies being born as homozygous merle. Sorry, I'm unfamiliar with coat colour genetics. Its not something I have ever had to worry about.

I'm sure I've read somewhere that such a mating would be unwise, but can't remember where. This article has info, but isn't written in layman's terms!

Thanks.... might take some deciphering ;-) but will surely put my A-level in genetics to good use :-D

Tanya, you may like this page which is about harlequin:
http://abnormality.purpleflowers.net/genetics/harlequin.htm
and this one is about double merles:
http://abnormality.purpleflowers.net/genetics/problems.htm
Great Dane colours:
http://abnormality.purpleflowers.net/genetics/danes.htm

Harli's are'nt usually put to Harli's, as it can cause white puppies who may be deaf!

http://www.dogstuff.info/inheritance_of_great_dane_coat_color_chopson.html

You are partly right, it is the piebald gene. Which is ONE cause of deafness.