A normal mammalian cell contains two copies of each set of genes, one inherited from the mother and one from the father. Unraveling what each gene does can be extremely complicated, especially when the two copies are dissimilar. It would be much simpler to determine gene functions if one could work with a cell that only had one set of genes. Martin Leeb and Anton Wutz of the University of Cambridge have managed to create just that.
Illustration of the chromosomal organization of haploid and diploid organisms.By Ehamberg, 5/10/2010
Haploidy, (containing only a single set of genes) is known in some species, but is never normally seen in adult vertebrates. Every cell in our bodies is diploid (with two sets of genes) except for our eggs or sperm. Leeb and Wutz modified a technique previously used on zebrafish in which either the eggs or sperm are irradiated to remove their genetic material prior to fertilization. The researchers successfully created haploid mouse cells for study or implantation into mouse embryos.
To be clear, the researchers did not grow up entire haploid mice, but mice containing patches of haploid cells. This is surprisingly useful. As Wutz explains:
These embryonic stem cells are much simpler than normal embryonic mammalian stem cells. Any genetic change we introduce to the single set of chromosomes will have an easy-to-determine effect.