American and Japanese scientists have genetically modified the sperm of a Zebra danio, grown it in a laboratory dish and produced a transgenic creature.
Dr Shawn Burgess, of the US National Human Genome Research Institute, said in the Proceedings of the National Academy of Sciences: "To our knowledge, this is the first time that sperm cells have been cultured entirely in vitro and used to produce a transgenic animal."
According to NewScientist.com, growing sperm in a test tube creates GM animals in one generation rather than two and may also allow scientists to do sophisticated genetic manipulations in a wide range of animals. So far these have only been possible in mice.