A team of scientists from the College of Life Sciences of Peking University found out that the fascinating milky coat of white tigers is due to a single change in a gene responsible for pigmentation in a variety of animals.
White tigers are not classified as species or sub-species of the big cats but are mutants of the orange Bengal tiger. According to a report on National Geographic, they were first recorded in the 1500s in India. The last of the wild white tigers was shot back in 1958. Today the captivating animals with blue eyes are mainstays of zoos and have been bred in captivity by individuals. In the 1970s, there were only a few left but breeding efforts have pushed its numbers back up to hundreds.
The Chinese scientists led by Xiao Xu from Peking University published their study titled "The Genetic Basis of White Tigers" on the Current Biology journal.
The experts compared the DNA samples from nine orange tigers and seven white tigers from the Chimelong Safari Park in China. They focused on the pigment gene known as SLC45A2 that has been linked to light coloration in humans and it some animals such as chickens, horses and fish.
"We conducted genome-wide association mapping with restriction-site-associated DNA sequencing (RAD-seq) in a pedigree of 16 captive tigers segregating at the putative white locus, followed by whole-genome sequencing (WGS) of the three parents. Validation in 130 unrelated tigers identified the causative mutation to be an amino acid change (A477V) in the transporter protein SLC45A2," the summary of the study explained.
The white tigers have a variant of the SLC45A2 that prevents the production of yellow and red pigments without affecting the production of black pigments. This explains why the majestic animals do not have the orange coats of its Bengal cousins but still have its dark stripes.
The SLC45A2 produces a kind of protein made up of 560 amino acids. A single mutation of the gene distorts the amino acids and prevents them from doing their part in the creation of yellow and red pigments.
The study also pointed out that a lot of white tigers in captivity suffer from some health problems such as deformities and eyesight problems. According to the scientists, these problems may be due to the inbreeding practices by humans. They reiterated that these animals can survive in the wild despite the mutation.
The proponents of the study consider the white tiger a good representative of the diversity of the big cats. They recommend that the orange and white tigers be used to up the population of Bengal tigers with reintroduction to the wild as a possible good move for tigers in general.