China is spending hundreds of billions of dollars annually in an effort to become a leader in biomedical research, building scores of laboratories and training thousands of scientists. But the rush to the front ranks of science may come at a price: Some experts worry that medical researchers in China are stepping over ethical boundaries long accepted in the West. Scientists around the world were shocked in April when a team led by Huang Junjiu, 34, at Sun Yat-sen University in Guangzhou, published the results of an experiment in editing the genes of human embryos.