2006-11-29 / Columnists

Pets, Pets, Pets

by Joanne Anderson

Powder, white Boxer, Powder, white Boxer, It's written that Noah built an ark to ensure zoological diversity. Back then, he didn't know (or care) that genes were the blueprints for life. He probably wouldn't have believed it. Being a typical man, he didn't take a map either. Scientists now have a new type of map- genome maps- to unravel the mysteries within the species Noah allegedly saved. Here are a few post-diluvian findings about genomes:

The typical mammal genome has about 24,000 genes. Cats have 38 chromosomes (19 pairs); dogs have 78 chromosomes (39 pairs); and humans have 46 chromosomes (23 pairs) - all with about 24,000 genes. That's not many in itself, but these are turned on and off in various combinations in different ways, multiplying the possibilities. Genes are inherited in blocks. With some species mapping already documented, scientists can search for genetic markers. They line chromosome profiles up- side by side, cut and paste, focus on tinier sections, and find similarities of position between inherited conditions in comparable species. For example, the defective gene for progressive retinal atrophy (PRA) was found on chromosome 9 in dogs before discovering it on chromosome 17 in humans.

Pebbles, Weaten/Shihtzu Pebbles, Weaten/Shihtzu Species might even have genes for traits they no longer have. A porpoise with leg stumps made headlines a few weeks ago. Genetic researchers (like Dr. Niels Pedersen of UC Davis who gave us a crash course in the feline/canine genome at the Cat Writers Conference in San Francisco last week) weren't shocked. Porpoises have about 24,000 genes and in this porpoise, the leg genes had failed to turn off.

The canine genetic sequence is complete. A Boxer named Tasha served as the model. All genes come as pairs- one from the mother and one from the father. The breed choice wasn't important because all dogs are about 99% identical at the DNA level. They wanted a dog with the most "homzygosity"- the least variation between maternal/paternal gene pairs. This highly inbred Boxer was chosen.

From a vial of Tasha's blood, 2.5 billion pieces of DNA, or genetic data, were reassembled in the proper order after researchers decoded each individual piece. To draw an analogy, scientists say it is like all of the pages of a book going through a paper shredder, each scrap analyzed, and then pasted back as proper pages.

The cat genome project is not finished yet. Scientists have sequenced "Cinnamon's" blood twice but will do so 4 more times to create the consummate map. Cinnamon is an Abyssinian, a breed with ancient roots, with a welldocumented pedigree. She's at the veterinary ophthalmology lab at the University of Missouri. She will go down in scientific history as one of the most important

cats that ever lived. In addition, findings from Cinnamon's genetic map may ultimately restore eyesight by curing PRA in humans and in her Abyssinian relatives.

Scientists can now identify genes for simple recessive traits like hemophilia. They are beginning to use genes to search for complex traits, such as canine hip dysplasia, a condition that Dr.Pedersen calls the researchers' "Holy Grail". People have about 5,000 genetic disorders with 1 in 500 affected; dogs have only 500 genetic disorders, but with 1 in 10 affected- manifested more in dogs because the defective genes surface via the many purebred lines.

Domestication plays a crucial role. Genome mapping helps to pinpoint the time when man intervened in a species' evolution. Dogs have been alongside us 14-17,000 years, whereas cats merely 4-7,000 years. With selective breeding, we have "shape shifted" dogs' look and purpose more than any other mammal. (Think companion Chihuahua vs. guarding Mastiff.) Cats are an excellent animal model to study because their genetic makeup has stayed consistent.

Researchers are examining certain behaviors as complex genetic traits. Can the pointing behavior in a sporting breed be traced to a block of genes? Where in the process of domestication does a wolf's stalking of prey turn into a Collie's herding of sheep? Perhaps the goal of taming is to perpetuate that Peter Pan relationship.

Is there a genetic component to the canine life span paradox? In mammals, usually the larger ones, like elephants, live the longest; the small ones, like mice, survive briefly. However the opposite is true in dog breeds. Small dogs tend to outlive the giant breeds. Why?

Manipulating genes and gene therapy may be the wave of the future. With these techniques, veterinarians have already restored the sight of 3 Briards with a hereditary retinal disorder and prolonged survival of 12 dogs with malignant melanoma. Pedersen says that every gene is a protein. Alter the protein, alter the gene, so drugs may be able to do that and the canine and feline maps open up new highways.

This week our poster dogs at Oyster Bay Town Shelter (677-5784) Miller Pl. Syosset don't want anyone to count their 78 chromosomes or chart their DNA. They just want someone to come see how endearing they are, so they can make their adoption plea. "Powder" #1129 is an 8 year old lovable, white Boxer. She has lived with kids. "Pebbles" #1093 is a 6-year-old Wheaten/Shihtzu. Her owner is terminally ill. She was very well-behaved for her grooming at the shelter. See more photos on the shelter's Petfinder site.

Males: "Bob"- the hefty tabby in the lobby window showcase;"Sarge" #1082- a big boned Shepherd mix; "Sebastian" #1119- a bent ear Shepherd who likes other dogs.

Female: "Kelly" #860- the gold Shepherd mix has been waiting a long time for a forever home.

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