The joy about zoos, is going to see the animals which you have read about in books. I would say once you have been to 1 zoo, you have been to them all! However in some situations, there are specialised species like the white Bengal tiger which is a rare genetic variant of the normal orange Bengal tiger sub-species.
These tigers can be found in their natural environment, the wild but they are far more common in captivity, where they are inbred to maintain the distinctive white coat colour. As a consequence of inbreeding, many of these captive white tigers have genetic mutations, or trouble with sight and hearing due to the loss of pigmentation.
The Peking university has reported in the journal of Current Biology, the genetics of a family of tigers in the Chimelong Safari Park. This study included both white and orange tigers. The study pinpointed the pigment gene SLC45A2. This gene inhibits the production of the red and yellow pigment, but the gene for black pigmentation remains unaffected and the stripes are still produced.
This genetic discovery is hoped to lead to their reintroduction into the wild under a conservation programme. It would appear that white tigers are more vulnerable than their counterpart Bengal tigers, where they are targeted for trophy hunting. All the white tigers which were shot were mature adults and suggests that these tigers are able to survive without their fitness being compromised.
So maybe, there will be more white tigers roaming free through the wild soon.