For these mice, there are two options.
Researchers at the University of Texas have bred mice from the genetic material of two male parents. How? Well, it’s a complicated process (although surprisingly this isn’t the first time it’s happened).
Mice—like humans—have either two X chromosomes or one X and one Y chromosome. In this case, the researchers reprogrammed a cell from a guy mouse to become an induced pluripotent stem (iPS) cell that can develop into any tissue in the body. These in turn become XO (genetically female) cells which were injected into early stage embryos and implanted into surrogate mothers.
The resulting baby mice were chimeras—like the Liger—with two genetically different cells either from an X chromosome from the original male mouse or an X or Y chromosome from the donor blastocyte (embryo).
These, however, weren’t the motherless mice. The females from the batch of chimeras were mated with a new male. As the females’ DNA was entirely derived from male genetic material, the resultant babies were, essentially, the product of two fathers.