Ethics do govern what is allowed in science. Some one also mentioned that every act has its own consequences. Because of this, ethics can never be separated from science. There should always be the Kantian question of the end justifying the means. Since there is no universal answer to this question, it must be applied to situations as they occur.
Ethics serve as a check on the power of scientific study.
Without the limitations that our ethics impose on science, scientists would have enough power to drastically alter the world as it exists today. Examples of this unregulated power lie in cloning as well as human and animal experimentation. As noted in previous responses to this question, ethics will always play a role in regulating scientific activities. Although it may be helpful to learn new things by unethical methods, the result of this experimentation and discovery could be devastating to our culture. Because of these risks, ethics will always be a part of science.