Siamese cats are heatmaps of themselves

Siamese cats are walking heatmaps. Their characteristic coloration results from a delightful mutation (maybe I should call it a mew-tation) in tyrosinase, an enzyme that makes melanin. A deleted cytosine amino acid causes a frameshift mutation. The result? Tyrosinase in Siamese cats is particularly sensitive to temperature, denaturing at normal body temperature.

This means that near the cat's warm body, the enzyme doesn't function, and melanin isn't produced. But at colder extremities like the tail, feet, ears, and face, the color kicks in.

When Siamese cats are born, their fur is white— which makes sense, considering the warm temperature of the womb. Within a few weeks, the color pattern emerges. As they age and naturally get less active, they also get darker, and color can be used to predict their age. There's a similar mutation in the tyrosinase of Burmese cats which occurs at a different genetic location than that of Siamese cats.

Here's my cat! I adopter her a few months ago and I think she's a blue point Tonkinese, which is a cross between Burmese and Siamese.