Cat lovers have long known that the distinctive three-toned calico patterning is almost exclusively found in female felines.
Now, the genetics behind that anomaly may help scientists understand human DNA a little better, too.
That's because calico cats may help explain so-called gene silencing -- flipping the "off switch" on genes, researchers say.
A team at the University of California, San Francisco say the unique orange-white-and-black patchwork fur on these cats is due to the silencing or inactivation of one of their two X chromosomes.
As the researchers explained, cells in female mammals have two copies of the X chromosome -- one from the mother and one from the father. Cells require only one active X chromosome, so the second one is turned off.
Calico cats have an orange-fur-color gene on one of their X chromosomes and a black-fur gene on the other. According to the UCSF team, the random silencing of one of the X chromosomes in each cell results in the calico cats' unique patchwork coat.
Scientists don't know exactly how a cell turns off a chromosome, so the researchers are trying to learn more about how different kinds of genes can be switched on or off without affecting the underlying DNA sequence.
This knowledge could lead to improved understanding, diagnosis and treatment of X-chromosome-related diseases in humans, said the researchers, who are scheduled to present their findings Tuesday at the Biophysical Society's annual meeting in San Francisco.
"Uncovering how only one X chromosome is inactivated will help explain the whole process of 'epigenetic control,' meaning the way changes in gene activity can be inherited without changing the DNA code," Elizabeth Smith, a postdoctoral fellow in the anatomy department at UCSF, said in an American Institute of Physics news release.
"It can help answer other questions, such as if and how traits like obesity can be passed down through generations," she said.
Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
The U.S. National Library of Medicine has more about the X chromosome.
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