Chromosome replication Essay example -- essays research papers

Precise chromosomal DNA replication during S level of the cell cycle is a crucial factor in the proper maintenance of the genome from generation to generation. The current once-per-cell-cycle model of eukaryotic chromosome duplication describes a highly coordinated process by which temporally regulated replicon clusters ar sequentially activated and subsequently united to form two semi-conserved copies of the genome. Replicon clusters, or replication domains, are comprised of individual replication units that are synchronously activated at predetermined points during S phase. Bi-directional replication within separately replicon is initiated at periodic AT-rich origins along separately chromosome. Origins are not characterized by any specific nucleotide sequence, but rather the spatial arrangement of origin replication complexes (ORCs). Given the duration of the S phase and replication fork rate, adjacent origins must be appropriately spaced to ensure the complete replication of each replicon. Chromatin arrangement by the nuclear matrix whitethorn be the underpinning factor responsible for ORC positioning. The six subunit ORC binds to origins of replication in an ATP-dependent manner during late telophase and early G1. In yeast, each replication domain simply contains a single ORC binding site. However, more complex origins are characterized by an initiation zone where DNA synthesis may begin at numerous locations. A single round of DNA synthesis at each activated origin is achieved by lic...