Merle and Mantle Merle
Many misconceptions regarding the merle colour exist. Now that the American Kennel Club is voting on making it a recognised show and breed colour, it is probably time to discuss these historical untruths.
Historically the breeders thought they could rid the breed of the colour by never breeding it. They had no knowledge of colour genetics and did not know that this is impossible, unless you want to rid the breed of harlequin as well.
Merle does not carry medical issues. Not any more than any other colour. What people do not realise is that a harlequin is a merle. Without merle there is no harlequin.
A dog with one merle gene is merle. A dog with one merle and one harlequin gene is a harlequin. A dog with two merle genes is mostly white and probably has one or more sensory defects. A dog with two harlequin genes does not exist. They are killed in embrio.
Thus breeding with a merle is the same as breeding with a harlequin. The secret is not breeding two merles (remember harlequin is also merle). Such breedings will result in double merles.