The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

Orc mutants arrest in metaphase with abnormally condensed chromosomes.

The origin recognition complex ( ORC) is a six subunit complex required for eukaryotic DNA replication initiation and for silencing of the heterochromatic mating type loci in Saccharomyces cerevisiae. Our discovery of the Drosophila ORC complex concentrated in the centric heterochromatin of mitotic cells in the early embryo and its interactions with heterochromatin protein 1 ( HP-1) lead us to speculate that ORC may play some general role in chromosomal folding. To explore the role of ORC in chromosomal condensation, we have identified a mutant of subunit 5 of the Drosophila melanogaster origin recognition complex ( Orc5) and have characterized the phenotypes of both the Orc5 and the previously identified Orc2 mutant, k43. Both Orc mutants died at late larval stages and surprisingly, despite a reduced number of S-phase cells, an increased fraction of cells were also detected in mitosis. For this latter population of cells, Orc mutants arrest in a defective metaphase with shorter and thicker chromosomes that fail to align at the metaphase plate within a poorly assembled mitotic spindle. In addition, sister chromatid cohesion was frequently lost. PCNA and MCM4 mutants had similar phenotypes to Orc mutants. We propose that DNA replication defects trigger the mitotic arrest, due to the fact that frequent fragmentation was observed. Thus, cells have a mitotic checkpoint that senses chromosome integrity. These studies also suggest that the density of functional replication origins and completion of S phase are requirements for proper chromosomal condensation.[1]


  1. Orc mutants arrest in metaphase with abnormally condensed chromosomes. Pflumm, M.F., Botchan, M.R. Development (2001) [Pubmed]
WikiGenes - Universities