His little Scottish terrier had a brain tumor, and it would be only a matter of time before the dog died. Like most in his shoes, Denniston just wanted to end the pain.
However, he took it one step further.
An expert in mammalian reproductive physiology, Denniston collected a tiny skin sample from the dog and took it to his laboratory at Louisiana State University, where he cultured it and froze it in liquid nitrogen.
From that idea, Denniston started Lazaron BioTechnologies, which will save pet DNA for $500, plus a monthly storage fee of $10, until cloning Fido becomes a reality.
Thanks mostly to the largess of an anonymous California multimillionaire, that day may not be so far off.
"It will happen," says Mark Westhusin, a Texas A&M professor of veterinary physiology leading a dog cloning team. "It could happen extremely soon if everything worked out."
Most experts put successful dog cloning a year to five years down the road. The cost is bound to be prohibitively expensive at first, but it would eventually come down to a few thousand dollars, says Carol Bardwick, the president of Canine Cryobank in San Marcos, California
"We've been putting up cells since Dolly made her debut," Bardwick says.
Dolly, the sheep that started it all, was the first clone ever produced from an adult mammal cell. When her existence was first announced in 1997, most biologists believed that cloning was decades in the future if it was possible at all.
Since then, cattle, goats, mice and monkeys have been cloned in labs, and pets are likely to be next.
"I really believe that the technology is going to become available for many species in the near future," Denniston says.
At least four companies are hoping to cash in on that technology
Lazaron, Canine Cryobank, perPETuate of Newington, Connecticut, and Genetic Savings and Clone of College Station, Texas.
When a pet owner contacts a gene bank, it will send a DNA collection kit. A veterinarian performs a routine skin biopsy, immerses the sample in a special transport medium and sends it to the gene bank.
At the bank, the skin cells are placed in a growth medium that causes them to divide a few times. Then they're frozen in liquid nitrogen at minus 376 degrees Fahrenheit.
Genetic Savings and Clone was founded by A&M's Westhusin and Lou Hawthorne, a documentary film producer, when a wealthy friend of Hawthorne's heard about Dolly and wanted to know if dogs could be cloned.
Hawthorne learned the process was a possibility, albeit a costly one.
The friend who insisted his identity remain a secret gave the go-ahead, and Hawthorne hired a scientific advisory board. In March 1998, he awarded Westhusin a $2.4 million grant for dog cloning research.
Dog cloning may be more appropriate, oddly enough, to lovable mutts than high-quaity purebreds, says Princeton University cloning authority Lee Silver.
Because mutts are unique and irreproducible creatures, cloning would be the only way to get anything like the original dog, Silver says.
A purebred, on the other hand, is a consistent product, genetically designed by years of careful breeding to come out the same every time.
Westhusin says there are still one or two major research issues to iron out.
For example, dogs are very stingy with their eggs, producing a batch only once every six months to a year. That means that until they can induce dogs to come into heat, the researchers only have a few eggs a week to work with.
Meanwhile, the DNA keeps coming.
"Certainly some of our customers are crazy," Hawthorne says. "But far more of them are simply crazy about their animals."