What trait dictates that both parents must carry the gene for a white cub to be born?

The recessive nature of the trait

The unusual white coloration exhibited by the tiger is governed by a specific pattern of inheritance known as a recessive trait. For a cub to physically manifest the leucistic white coloration, it must inherit the gene variant responsible for this trait from both of its biological parents. If only one parent carries the gene, the cub will typically appear orange, possessing the camouflage coloration of a standard Bengal tiger, even though it carries the hidden, recessive gene. This requirement for two copies of the rare gene is precisely why the trait is so uncommon in natural settings, where the chance of two carriers meeting and breeding was historically very low, estimated at only about one in every 10,000 births.