Stem Cell Mixing May Form a Human-Mouse Hybrid.

Dr. Irving L. Weissman, an expert on stem cells at Stanford University, said that making mice with human cells could be “an enormously important experiment,” but if conducted carelessly could lead to outcomes that are “too horrible to contemplate.” He gave as an extreme example the possibility that a mouse making human sperm might accidentally be allowed to mate with a mouse that had made its eggs from human cells.

[Insert witticism about parents being mice here].