The mystery behind the orange coat colour in cats has been solved after more than 110 years of research. Orange, or ginger cats, were historically seen in Egyptian art and have featured in popular culture characters like Garfield and Puss in Boots. While most cats have brown or grey tabby coats, ginger cats are distinct for their vibrant orange colour. Tortoiseshell cats, on the other hand, display a mixture of orange and non-orange hairs, creating a unique brindling pattern.
For decades, scientists were unsure of the genetic cause behind these coat colours. In 1912, American geneticist Clarence Cook Little proposed a theory involving the X chromosome, which later proved to be true. He suggested that female cats, having two X chromosomes, could be tortoiseshell due to the presence of both orange and non-orange forms of the X chromosome. Males, with just one X chromosome, could either be orange or non-orange but not tortoiseshell.
Now, two independent research teams—one from Japan and another from the US—have discovered the gene responsible for the orange coat colour, located on the X chromosome. Known as the “Orange gene” (ARHGAP36), this gene plays a role in pigment production. A deletion in part of this gene causes the orange coat colour, while the unchanged form results in the non-orange colour.
These discoveries confirm Little’s theory and open new avenues for research into hair follicle and pigment development in mammals.
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