Males beware. Researchers have produced live mice by parthenogenesis. That means no sperm, no male chromosomes and no need for males. The study is described in the 22 April 2004 issue of Nature (Vol. 428, No. 6985, pp. 860-864).
Some insects and reptiles can reproduce by parthenogenesis, in which the unfertilized egg retains two sets of chromosomes and begins to develop as if it had been fertilized. In mammals, though, successful parthenogenesis has been regarded as virtually impossible - unfertilized eggs can be jolted into life, but the resulting embryos do not develop.
Now Tomohiro Kono and colleagues have produced parthenogenetic mice that can develop to adulthood. The first parthenogenetic pup, 'Kaguya', grew to be a healthy adult female who reproduced normally. The mice developed from eggs that contained maternal genetic material only. The team knocked out a key gene in the donor egg, and so affected imprinting - the process by which one of two copies of a gene is turned off.
The study shows that imprinting influences the developmental potential of parthenogenetic embryos. "Taken as a whole, the work of Kono et al. provides good evidence that incorrect expression of imprinted genes is one of the major reasons why natural parthenogenesis in mammals has not been possible," say David A. F. Loebel and Patrick P. L. Tam in an accompanying News and Views article.
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