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August 5, 2005

Why cats don't like sweets

Cheetah

Long story short: they can't taste them.

Last month scientists from the Monell Chemical Senses Center in Philadelphia published a paper demonstrating that all cats — both the big ones of the jungle and the puddy tat curled up on a ball next to you on your pillow — harbor a genetic mutation rendering the sugar detectors on their taste buds inoperable.

The sweetness receptor in taste buds consists of two different proteins, T1R2 and T1R3, attached to each other on the surface of a cell.

The two proteins are manufactured under the direction of two genes, then join to create a single receptor that fires a nerve signal up to the brain when sugar is present.

The scientists found that in cats one of those two genes — called Tas1r2 — is missing a stretch of 247 DNA base pairs, a deletion that prevents the gene from making a correctly structured T1R2 protein.

With only one of the two crucial proteins, the receptor cannot function and the cat cannot taste sweetness.

Though the gene sequencing was done on six house cats (all pets of Monell scientists), when the scientists looked at tiger and cheetah DNA they found the same genetic deletion.

This suggests that the mutation occurred in a common ancestor early in feline evolution.

"It isn't clear whether the cat's loss of its sense of sweetness led it to pursue an all–meat diet or whether cats were already fully carnivorous, in which case the loss of an affinity for sweets would hardly have mattered to them," wrote Rick Weiss in a Washington Post story on July 25.

Here's a link to the original paper.

August 5, 2005 at 10:01 AM | Permalink


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