If, by applying transgenic technology to mice, human beings grew mouse ears, and if this human being happened to be your long-missing younger brother, how would you feel?
Background information: Humans are currently "growing" human ears on mice using transgenic technology. Once this technology matures, all of humans' organs in the future could be cultivated as "backups" on other animals, and the problem of a lack of human organs would be significantly alleviated.