A mutated gene holds clue
WHITE tiger is the most charismatic species of all. However, this rare variant of the orange Bengal tiger (Panthera tigris tigris) can be seen only in zoos. It is said that white tiger is the result of a genetic defect, which does not allow them to survive in the wild.
Researchers from China and South Korea recently studied this speculation and have acquired insight into how white tigers got their colour.
They mapped genomes of a family of 16 tigers living in Chimelong Safari Park in Panyu, Guangzhou Province. The 16 tigers included both white and orange individuals. The researchers sequenced the genomes of the three parents in the family and zeroed in on the gene that codes for synthesis of pigments. The gene has long been associated with the light colour seen in some human population and in other animals, including horses. They identified a mutation in the white tiger version of the gene, which appeared to inhibit the synthesis of red and yellow pigments.
This change has no effect on the synthesis of black pigment, explaining why the tiger still has the characteristic dark stripes on the white fur. The study was published in Current Biology on June 3, 2013. Usually white tigers found in zoos have health issues, such as premature death, low fertility, stillbirths and deformities such as shortened legs, arching of the backbone and eye weakness. However, Shu-Jin Luo, one of the authors from Peking-Tsinghua Centre for Life Sciences of Peking University, Beijing, says the problems are a result of inbreeding and not mutation.
K Ullas Karanth, director of Centre for Wildlife Studies in Bengaluru, says the study is of theoretical interest. “White tigers have no conservation significance. They are like humans with some inherited genetic deficiency.
The study does nothing to help the recovery of declining tiger populations in the wild.” The team advocates a proper captive management programme to maintain a healthy Bengal tiger population, including both white and orange individuals. They say it might be worth considering reintroduction of white tigers into their wild habitat. After all, historical records dating back to the 1500s suggest white tigers were found in the wild in the Indian subcontinent—the last free ranging white tiger was seen in 1958.
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