Sperm plus an egg is the basic equation to start fertilization but scientists have achieved what was once thought of as impossible. They were able to produce live mice without requiring a sperm to fertilize an egg cell. The breakthrough could one day allow men and women to self-fertilize to produce a biological offspring.

For the breakthrough research reported in the journal Nature Communications on Sept. 13, Tony Perry, from the University of Bath, and colleagues used chemicals to stimulate unfertilized eggs so these would act as if they had been fertilized. Within 16 hours, the eggs started to make changes to their DNA in preparation for producing the hundreds of different cell types that are present in mice.

Mammals need DNA from both the egg and sperm so they can develop properly and since the chemically stimulated embryos used in the experiment only had half the genetic complement needed for development, the process eventually stopped.

When the researchers injected genetic material from the sperm into the fake embryos at this stage, they found that they started to act as if the sperm and the egg have been united from the start of the process.

In the experiments, the non-traditional embryos produced baby mice 24 percent of the time. The mice were also healthy, went on to live as long as normal mice and were even able to produce additional two generations of mice.

"Developmentally incompetent haploid embryos (parthenogenotes) injected with sperm developed to produce healthy offspring at up to 24 [percent] of control rates, depending when in the embryonic cell cycle injection took place," Perry and colleagues wrote in their study.

"This implies that most of the first embryonic cell cycle can be bypassed in sperm genome reprogramming for full development."

Perry said that the result of their experiments challenges the long-held dogma that only an egg cell that was fertilized with a sperm cell can produce live mammals.

"This is first time that full term development has been achieved by injecting sperm into embryos," Perry said. "It had been thought that only an egg cell was capable of reprogramming sperm to allow embryonic development to take place."

The result also hints that it may one day be possible to produce live animals using non-egg cells and sperm. While this is currently only an idea, it may have potential implications in human fertility treatments and in breeding endangered species.

Paul Colville-Nash from the Medical Research Council (MRC), which funded the research, said that the research can shed light on how human life begins and what influences the viability of embryos.