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Man's Genetic Best Friend

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This article was written for CBSNews.com by Muni S. Jaitly.

Dogs may be better friends than we think.

Scientists from the Broad Institute of Harvard and Massachusetts Institute of Technology announced last week the successful high-density sequencing of the dog genome. The genome sequence was published in the Dec. 8 issue of the journal "Nature."

Many geneticists believe the dog genome, in comparison with the human genome, will shed light on how dog and human diseases work. Studies could lead to new treatments of diseases like cancer and diabetes. The human genome was sequenced in 2003.

Dogs, after humans, suffer from the second greatest number of inherited genetic diseases in mammals. The canine genome is an ideal model for studying genetic diseases in both dogs and humans because so many of the diseases overlap.

"With the click of a button we can go to a chromosome, sub region or gene. From human to dog," said Dr. Elaine A. Ostrander, chief of the Cancer Genetics Branch at the National Institutes of Health. She is also co-editor of "The Dog and Its Genome," published by Cold Spring Harbor Laboratories Press.

A genome is like a recipe. It is an organism's complete set of deoxyribonucleic acid (DNA). DNA is the chemical compound in an organism that carries genetic information — the molecule of heredity. Genes are regions of DNA passed on from parent to offspring. In dogs, DNA determines traits like coat color, limb strength and disease susceptibility.

Dr. Martin L. Katz, professor of ophthalmology at the University of Missouri-Columbia, compared genes and genomes to books in a library.

"You look for a book, read it and master it. Then you compare two books from different libraries word for word and tell the differences," he told CBS News. The difference between genomes of a healthy and unhealthy organism can determine disease.

Once the genes responsible for disease have been identified, researchers can perform one of two procedures on the organism: gene replacement or gene repair therapies.

Both therapies are like fixing a car: you can get a new engine or simply fix the old one. In gene replacement therapy, an artificial gene, without the disease-causing mutation, replaces the disease-causing gene in the cells of the organism. In gene repair therapy, geneticists try and repair the mutation within the gene.