All chromosomes must be completely replicated prior to cell division, a requirement that demands the activation of a sufficient number of appropriately distributed DNA replication origins. Here we investigate how the activity of multiple origins on each chromosome is coordinated to ensure successful replication. We present a stochastic model for whole chromosome replication where the dynamics a...

Chromosome segregation in the bacterium Caulobacter crescentus involves propulsion of the replication origin and its capture at one pole of the cell. Bowman et al. (2008) and Ebersbach et al. (2008) now report the discovery of a protein called PopZ that mediates this chromosome capture.

The origin recognition complex (ORC) is conserved in all eukaryotes. The six proteins of the Saccharomyces cerevisiae ORC that form a stable complex bind to origins of DNA replication and recruit prereplicative complex (pre-RC) proteins, one of which is Cdc6. To further understand the function of ORC we recently determined by single-particle reconstruction of electron micrographs a low-resoluti...

We show that in fission yeast the mitotic B type cyclin Cdc13/Cdc2 kinase associates with replication origins in vivo. This association is dependent on the origin recognition complex (ORC), is established as chromosomes are replicated, and is maintained during G2 and early mitosis. Cells expressing an orp2 (ORC2) allele that reduces binding of Cdc13 to replication origins are acutely prone to c...

Presence of toxic metals in agricultural soils can impose adverse health impact on consumers. The main purpose of this study was to determine spatial distribution of elements Fe, Sb, Mn in agriculture soils and crops of Hamedan Province in Iran. Soil samples (0-20 cm depth) were collected from an area of 2831 km2.  Iron, Antimony and Manganese in samples of soil and agricultural crop...

MicroRNA is no longer the ‘new kid on the block’ although for a long time they were considered such. MicroRNA is a general term for a big family, which increases by the day, of non coding RNA. Their functions are mainly to emulate gene expression. The old dogma was that from DNA to transcription of mRNA and then translation to protein. Today we know that from DNA there is a step in which microR...

A s the periodic bloodshed continues in the Middle East, the search for an equitable solution must come to grips with the root cause of the conflict. The conventional wisdom is that, even if both sides are at fault, the Palestinians are irrational “terrorists” who have no point of view worth listening to. Our position, however, is that the Palestinians have a real grievance: their homeland for ...

In the framework of conditional, not necessarily orthogonal, term rewriting systems, we introduce the notion of an origin. Origins are relations between subterms of intermediate terms which occur during rewriting, and subterms of the initial term. Origin tracking is a method for incrementally computing origins during rewriting. Origins are a generalization of the well-known concept of residuals...

The initiation of DNA replication is a complex, multistep process with important implications for genomic stability. In this issue, Wu and Nurse (2009) find that initiation factors are differentially recruited to replication origins. They uncover evidence suggesting that the efficiency of this recruitment may determine whether and when an origin is used to initiate DNA replication in S phase.