KIE: Embryonic stem cells (ES cells) are derived from preimplantation blastocysts and can be subjected to genetic manipulation, allowing for the creation of intraspecies and transpecies animal chimeras. Given the effects of this research on the animals involved and the potential implications of future research, particularly in humans, is it ethical to proceed with research using ES cells or chimeras? Macer believes that though a more thorough examination is needed of the ethical implications of breeding mutated, transgenic, and chimeric animals, experience shows that limits can be placed on research when needed. Balk sees no ethical challenges to ES cell research as it is now conducted, but forsees future problems if attempts are made to alter human behavior. Freedman and Goulet argue that genetic manipulation is awesomely different from other kinds of research and treatment, requiring new principles of reasoning and an ethics of change.