Mice that had two fathers were also born but survived for only a couple of days. The work hinged on using genetic editing techniques to tackle “genomic imprinting” — a mechanism in mammals that means DNA must usually be present from a mother and father to create healthy offspring.
Experts said that the concept was intriguing for its possible application to human reproduction. They warned, however, of formidable ethical concerns and technical challenges.
The researchers were trying to answer fundamental questions about why we have sex. Mammals can make babies only through sexual reproduction – aka you need an egg from mum and a sperm from dad.
But the rest of the natural world doesn’t play by the same rules; some female fish, reptiles, amphibians and birds can go it alone.
The aim of the Chinese researchers was to work out which rules of reproduction they needed to break to make baby mice from same-sex parents. That in turn helps understand why the rules are so important.
It was easier with double mums. The researchers took an egg from one mouse and a special type of cell – a haploid embryonic stem cell – from another. Both contained only half the required genetic instructions or DNA, but just bringing them together wasn’t enough.
The researchers had to use a technology called gene editing, to delete three sets of genetic instructions to make them compatible (more on that later). The double-dad approach was slightly more complicated.
It took a sperm, a male haploid embryonic stem cell, an egg that had all of its own genetic information removed and the deletion of seven genes to make it all work. 📷: BBC