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The origin of replication (also called the replication origin) is a particular sequence in a genome at which replication is initiated. [1] Propagation of the genetic material between generations requires timely and accurate duplication of DNA by semiconservative replication prior to cell division to ensure each daughter cell receives the full ...
The origin recognition complex (ORC) is a highly conserved six subunits protein complex essential for the initiation of the DNA replication in eukaryotic cells. Studies in yeast demonstrated that ORC binds specifically to origins of replication and serves as a platform for the assembly of the pre-replication complex, which includes additional initiation factors such as Cdc6 and Mcm proteins.
These 100-200bp sequences facilitate replication activity during S phase. ARSs can be placed at any novel location of the chromosomes of budding yeast and will facilitate replication from those sites. A highly conserved sequence of 11bp (known as the A element) is thought to be essential for origin function in budding yeast. [27]
A licensing factor is a protein or complex of proteins that allows an origin of replication to begin DNA replication at that site. Licensing factors primarily occur in eukaryotic cells, since bacteria use simpler systems to initiate replication. However, many archaea use homologues of eukaryotic licensing factors to initiate replication. [1]
Because a new Mcm complex cannot be loaded at an origin until the pre-replication subunits are reactivated, one origin of replication can not be used twice in the same cell cycle. [ 32 ] Activation of S-Cdks in early S phase promotes the destruction or inhibition of individual pre-replication complex components, preventing immediate reassembly.
Recognition of the origin of replication is a critical first step in the formation of the pre-RC. In different domains of life this process is accomplished differently. In prokaryotes, origin recognition is accomplished by DnaA. DnaA binds tightly to a 9-base pair consensus sequence in oriC; 5' – TTATCCACA – 3'.
Under apt origin of replication (ori), it can replicate as a plasmid. It is normally used to clone large DNA fragments between 28 and 45 Kb. [6]
The initiator is the protein that recognizes the replicator and activates replication initiation. [1] Sometimes in bacteriology, the term "replicon" is only used to refer to chromosomes containing a single origin of replication and therefore excludes the genomes of archaea and eukaryotes which can have several origins. [2]