By Maggie Fox, Health and Science Editor

WASHINGTON, Oct 31 (Reuters) - The first full genetic map of a cat -- a domestic pedigreed Abyssinian -- is already shedding light on a common cause of blindness in humans and may offer insights into AIDS and other diseases, researchers reported on Wednesday.

And the cat genome shows some surprising qualities that cats and humans appear to have uniquely in common, the researchers report in the journal Genome Research.

"We can start to interpret them in terms of one of evolution's special creations, which is also probably one of the greatest predators that ever lived," Dr. Stephen O'Brien of the U.S. National Cancer Institute, who helped lead the study, said in a telephone interview.

The cat, named Cinnamon, is descended from lab cats bred to develop retinitis pigmentosa, a degenerative eye disease that causes blindness and which affects 1 in 3,500 Americans.

O'Brien said a study of her genes can help uncover some of the causes of the incurable condition and may help find treatments for it.

Cats also are important for studying other diseases, O'Brien said. "The reasons why the cat genome is cool go on for about an hour," he said.

For instance, they are the only animals besides humans who naturally become sick from immune deficiency viruses. People get HIV, which causes AIDS, while the feline immunodeficiency virus or FIV causes a similar disease in cats.

The discovery of feline leukemia virus in the 1960s led scientists to realize that viruses can cause cancer.

"This led to oncogene development and some of the best smart drugs that we have for cancer," O'Brien said.

TRACING EVOLUTION

Like other mammals, the cat has around 20,000 genes. Genome researchers have learned that much of the genetic code is made up of "non-coding regions" of DNA. These are stretches of DNA that do not make up genes but which are clearly important for biology.

Researchers can compare the cat genome to those of the six other mammal genomes that have been finished -- the human, chimpanzee, mouse, rat, dog, and cow -- to figure out differences in biology, evolution and disease.

O'Brien said this comparison already demonstrates something interesting that happened as so many different species evolved from a tiny, shrewlike ancestor that outlived the dinosaurs.

"The order of genes in cat is remarkably similar to the order of genes in the ancestor of all placental mammals," he said.

"The two species that have that similarity are humans and cats. Other species have a reshuffled genome, like a deck of cards. The cat and the humans are pretty much similar to the way it was, which means the good model didn't get fiddled with," he added.

Pedigreed cats and dogs are highly inbred, and Cinnamon especially so.

"We now, for the first time, have seen in the kind of detail that we never imagined a generation ago all these genes that this cat has as well as the footprints of inbreeding as well as cat domestication," O'Brien said.

According to The Humane Society, Americans keep 90 million cats as pets.

"One thing I'd like to discover is the genes for good behavior in the cats -- the genes for domestication, the things that make them not want to kill our children but play with them," O'Brien said.

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