The genetic basis of white tigers

Xu and colleagues identified the molecular cause of the white tiger phenotype, mapping it to a single amino-acid change in the pigment gene SLC45A2. Using a captive pedigree and genome analysis, they showed white colour is a recessive variant that reduces red and yellow pigment but leaves the dark stripes. Crucially, the variant is not inherently linked to ill health, meaning the deformities and disorders common in white tigers, such as crossed eyes, spinal and immune problems, stem from the intense inbreeding used to fix the colour, not the colour gene itself. The work clarified a long-running welfare controversy, supporting positions that white-tiger breeding for novelty perpetuates harmful inbreeding rather than conserving a natural variant.