Scientists have practically obliterated the ultimate symbol of maleness in DNA, the Y chromosome, and believe they may be able to do away with it completely.
They condensed all the genetic information normally found on a mouse's Y chromosome to just two genes.
Their study, in the journal Science, showed the male mice could still father babies, albeit needing advanced IVF.
The team in Hawaii argues that the findings could one day help infertile men with a damaged Y chromosome.
DNA is bundled into chromosomes.
In most mammals, including humans, one pair act as the sex chromosomes.
Inherit an X and Y from your parents and you turn out male, get a pair of Xs and the result is female.