Name: 暹羅貓背後的快樂變異 (The Delightful Mutation Behind Siamese Cats)
Uploaded: 2021-01-14T10:50:36.000Z
Duration: 3 min 46 s
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From a tiger's stripes, to a jaguar's rosettes, to a tabby's whorls, cats come

in lots of different colors and patterns.

Normally, we imagine that the way an animal looks is inherited from its parents — basic

But sometimes, the origin isn't so simple.

Like, the coloring of some domestic cats is tied to their sex.

That's why orange cats are much more likely to be males, and calicos and torties are almost

But Siamese cats are especially interesting — because their recognizable coloration

Animals get their dark color because their bodies produce melanin.

Melanin is the same protein responsible for

variation in human skin tone and making you tan.

And it's produced thanks in part to the enzyme tyrosinase.

Normally, this enzyme does its job pretty well.

But in some breeds of mouse, rabbit, and cat — and even in some human cases — the

In particular, virtually all Siamese cats have a mutated version of the gene that codes

So their tyrosinase is extremely sensitive to temperature.

So sensitive, in fact, that it unfolds and no longer functions at the average cat body

That isn't great for the enzyme - can't really do its job anymore - but it does

Without functional tyrosinase, no melanin gets produced, so most of the animal's fur

is a creamy white: It's essentially albino.

Siamese cats also have those super cute boots and that little brown mask.

And that's because tyrosinase is functional in their extremities, like their tails, legs,

Compared to their volume, these parts of the body have a larger surface area for heat to

escape from, so these small and slender body parts lose heat more quickly than the cat's

This is just like how your fingers and feet and nose are the first things to get cold

Or how a narrow icicle is going to melt before a compact ice cube made of the same volume

In a cat, this means the face, limbs, and tail are just a few degrees cooler compared

And that difference is enough to preserve delicate tyrosinase's shape and function,

If you ever get to see a newborn Siamese kitten, you can actually watch this process happen

When the cats are born, they're totally white, since the inside of the womb is a uniform

Out in the world, though, the temperature around the kitten is cooler than its body,

so it loses heat to the environment — /especially/ from its tiny toes and tail.

Within a few weeks, the characteristic Siamese color pattern starts to emerge as new fur

grows and tyrosinase gets to work in the cat's extremities.

So unless you're keeping mittens on your kittens, Siamese cats will develop their trademark coloration

Thanks for watching this episode of SciShow!

And special thanks to our patrons on Patreon — especially everyone who keeps sharing

their amazing animal photos in the floofs channel on our Discord.

If you want to join in the fun and help us keep making educational videos like this,

You can learn more at patreon.com/scishow.