If you want to know whether your new fluffy puppy will be a cuddly friend or snarl at and bite anything that moves, you might want to check out the length of its genes. Researchers at the University of Tokyo in Japan asked 100 Akita owners to fill out questionnaires about whether their pooches were naughty or nice. When they looked at the doggies' DNA, the scientists found that the meanest males more often had a shortened gene for a receptor that responds to various male hormones. The gene variant produces a form of the protein that has previously been shown to respond more strongly to testosterone. This is the first time that canine aggression has been associated with genetic differences in the male hormone receptor, the researchers report in Biology Letters this week. Over half of the Akitas they studied had this variant. Yet mean female dogs weren't more likely to have the short variant than the gentle dogs, suggesting that females respond differently to these hormones.
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