If a black dog and a white dog have puppies, what color will the puppies be? Genetic scientists have been trying to answer this question for hundreds of years. Genetics is the science of heredity-how traits are passed from parents to offspring. One of the first breakthroughs came from Gregor Mendel, a nineteenth-century monk who spent eight years breeding thousands of pea plants. Pea plants might seem pretty different from dogs, but on a microscopic...