Calico Cats Help Cure Curiosity

CalicoSniffingFlower_SpringRompContest_AmyMortensen_2011-04-20 Have you ever been curious about how calico cats get their multicolored fur?

It actually takes place during gestation, and is the result of a process called “X-chromosome inactivation” (or XCI), which has given researchers some amazing insights into the genetic behavior of all mammals.

Nearly every living organism on earth carries DNA, which is the self-replicating double-helixed material that determines genetic characteristics. In humans, cats, and other mammals, DNA is made up of several pairs of chromosomes. Each pair contains one chromosome from the organism’s mother, and one from the father.

There are some exceptions, but generally these chromosomes determine the organism’s gender. “X” chromosomes are found in both males and females, whereas “Y” chromosomes are found only in males.

The “X” chromosome, however, contains much more genetic information than the “Y,” which in females can lead to conflicting “X”-related genetic traits within a single cell’s DNA.

Fortunately, mammals have found a way to correct this problem with XCI. Female calicos, for instance, have two “X” chromosomes with conflicting fur-color traits. During the development of the cells that determine the color of their fur, each cell must determine which gene to express, orange or black, and which to deactivate.Cat_Josh

That’s what gives calico cats their beautifully motley coat, and why almost every calico is female.

Although research is just beginning on how this genetic phenomenon can be used to deactivate unwanted traits in humans (don’t worry: no one is trying to turn calico cats solid orange or anything), there is some speculation that, with a little more understanding, we might be able to wield XCI to disable obesity-related traits, and combat “X”-linked disorders like hemophilia and muscular dystrophy.

So next time you pet your calico (or someone’s), be sure to thank her for showing us how to combat “X”-linked genetic disorders. She’ll know what you mean.

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