Fact Box: What gives some tigers white fur with dark or sepia brown stripes ?
Scientists from Peking University, Beijing, have solved a long standing enigma behind the cause that gives some tigers white fur with dark or sepia brown stripes. It has been found that a change in a single amino acid (A477V) in one pigmentation-related gene (SLC45A2) adds this attribute in some tigers like White Bengal tigers.
What forms this color?
The color of the fur, stripes and eye of the tiger is determined independently by two types of melanin — pheomelanin and eumelanin. In the case of white tigers, only the pheomelanin that produces the red to yellow colour is affected. Eumelanin gives the black to brown colour and is unaffected, the reason why the eye and hair in the stripes are dark or sepia brown.
How does it happen?
Point mutation in the amino acid partially blocks a particular channel, as a result of which the yellow pigment-forming process gets affected. Incidentally, mutations in the same pigmentation-related gene (SLC45A2) causes light skin colour in modern Europeans, as well. Mutations in the same gene causes skin lightening in some mouse, horse, and chicken, the scientists point out. As this mutation affects only the pigmentation process, it probably has no role in causing deaths.