What specific pigment responsible for the orange hue is prevented by the SLC45A2 mutation?

Pheomelanin

The striking difference between a standard orange Bengal tiger and a white tiger is traced back to a molecular mechanism governed by the SLC45A2 gene. In standard tigers, this gene codes for a transport protein that functions correctly, allowing for the expression of pheomelanin. Pheomelanin is the specific pigment responsible for producing the reddish-orange color across the tiger’s coat. However, in white tigers, a point mutation occurs in the SLC45A2 gene, effectively halting or severely reducing the functionality of this transport protein. Consequently, the animal cannot express pheomelanin in the areas where it should appear, resulting in the lack of orange coloration, while the melanocytes responsible for the black stripes remain unaffected.