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For decades, dog lovers have been incorrectly calculating age of their pet pooches. People have traditionally worked out their dog's age in "human years" by multiplying by seven. However, researchers at University of California San Diego School of Medicine in USA have come up with new formula. They say it more precisely determines canine age. Their new method requires little more than simple mental arithmetic to work out dog's age. It involves comparison of genomes of dogs and humans. Scientists had to analyse how DNA changes as humans and dogs age. scientists regard such DNA analysis as best way to measure the ageing speed of mammals.

researchers analysed blood samples from 105 Labrador retrievers. After bit of number crunching, they created graph to show different rates at which canines and humans age. They said one-year-old dog is similar to 30-year-old human, while four-year-old hound is comparable to a 52-year-old person. Researcher Trey Ideker said by time a dog reaches seven years old, its ageing slows. He said: "This makes sense. When you think about it, a nine-month-old dog can have puppies, so we already knew that 1:7 ratio wasn't accurate measure of age." The researchers said their new formula doesn't fully address the fact that different breeds of dog age at different speeds.

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