Researchers Create Mice With 2 Daddies

Scientists at the University of Texas have managed to create mice from the genetic material of two males. A female mouse was involved, of course—researchers engineered one whose eggs contained only DNA from a male, then mated her with another male—but genetically the mice have two fathers. Scientists touted the procedure as “a new form of mammalian reproduction,” though the Wall Street Journal says that its “practical benefits are far from clear.”

“It has been a weird project, but we wanted to see if it could be done,” says the study’s lead author. To make it work, scientists took cells from a male mouse, turned them into something similar to embryonic stem cells, and then grew copies in a cell line until a small number—about 1%—spontaneously lost their Y chromosome. These cells were injected into early-stage embryos, and then transferred to surrogate mothers to create “chimeras,” meaning females that produce eggs with male DNA. (More genetics stories.)