Inheritance of tweed, a modification of merle, in Australian shepherd dogs.

An autosomal mutation is responsible for the modification of merle coat color (previously indicated to be due to a transposable DNA element) to the tweed merle pattern in the Australian shepherd dog. The tweed merle pattern consists of color patches that have a greater range in the intensity of the dilute patches and tend to be larger than the patches of nontweed merle. It has no action on nonmerle dogs. The symbol Tw is proposed for this gene.