Fig. 1: A proposed hypothesis of the genetic structure of sheep tail patterning based on the currently known, significant four genomic signatures.

The upper panel shows the main five sheep tail phenotypic patterns, including the long-thin tail (e.g., Merino sheep), short-thin tail (e.g., Tibetan sheep), long-fat tail (e.g., Chinese Large-tailed Han sheep), short-fat tail (e.g., Chinese Hu sheep), and fat-rumped tail (e.g., Kazakh sheep). Note: Sheep tails characterized by intermediate tail length and level of fat deposition are shown in some breeds. This intermediate pattern of the fat tail can be categorized between the long-fat tail and the short-fat tail (shown in the third and fourth tail phenotypic patterns in the upper panel). The lower panel shows the main candidate genes/regions of the sheep tail phenotype (in brown boxes). These include two genes linked with the sheep tail length [HOXB13 (refs. ^21,23) and TBXT (refs. ^16,17,18)] and two genes/regions linked with the fat-tail phenotype [PDGFD (refs. ^1,11,12) and the intergenic region between BMP2 and HAO1, referred to as the IBH region^13,14,15]. Yellow, red, and gray boxes indicate ancestral allele, derived allele, and currently unknown functional role, respectively. The icons of sheep tails used to construct this figure were adapted from Kalds et al.³.