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Scientists have engineered mice with two fathers as genetic parents, with no DNA from a mother. Researchers accomplished this feat through a series of complicated reproduction tricks, and though the result is indeed a scientific marvel, the question remains: Why even bother? The techniques involved, Wired's Brandon Keim writes, "are still far from practical or legal human use--and may never be used."

What were the not-yet-legal techniques? Discover's Andrew Moseman explains:

Behringer's team started with a single male mouse. Let’s call him Fred. Scientists took cells from Fred and transformed them into a line of induced pluripotent stem cells, which can grow into any kind of cell in the body. ... When the researchers created these stem cells, some of them--about 1 percent--lost the Y chromosome through ordinary mistakes that happen in cell division.

Thus, the scientists had a batch of Fred-derived stem cells that had no Y, and thus were labeled XO cells. The next step was to take ... early stage embryos that had been conceived in the traditional fashion--and inject the XO cells into them. When this XO-injected embryo was implanted into a normal female mouse, she gave birth to offspring called chimera--what we call animals with two or more genetically distinct populations of cells. In this case the mouse possessed, in addition to the normal cells from its mother and father, some XO cells derived from Fred. Finally ... some of the chimera mice would be female. And some of those females would have egg cells that derived from the XO cells. Let's say a female mated with a typical male mouse, Tom, and conceived with an XO egg: The resulting little one, be it a male or a female, would have been born of a female but possess genetic material from two males: Fred and Tom, mice two dads.

Researchers admitted their techniques needed "significant requirements" before they could be used on people. Moseman says that won't happen for a long time. "Even if one could imagine skirting the mad science aura and ethical quandaries of attempting such a thing, there are huge scientific hurdles to making it a safe way to conceive children," he writes.

As Joe Gandelman notes, "stay tuned for more developments--and controversy--as this new twist takes on its own life later in this 21st century."

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