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After introducing a nick in the system, the negative supercoil gradually unwinds (c) until it reaches its final, circular, plasmid state (d). [2] Nicked DNA can be the result of DNA damage or purposeful, regulated biomolecular reactions carried out in the cell. During processing, DNA can be nicked by physical shearing, over-drying or enzymes.
Using the unnicked strand as a template, replication proceeds around the circular DNA molecule, displacing the nicked strand as single-stranded DNA. Displacement of the nicked strand is carried out by a host-encoded helicase called PcrA (the abbreviation standing for plasmid copy reduced) in the presence of the plasmid replication initiation ...
It catalyzes the unwinding of double-stranded plasmid DNA that has been nicked at the replication origin by the replication initiation protein. Genetic and biochemical studies have also shown that the helicase plays an important role in cell-survival by regulating the levels of RecA-mediated recombination in Gram-positive bacteria.
Eukaryotic DNA replication is a conserved mechanism that ... required for the unwinding of plasmid DNA. ... Rad17 are able to recognize gapped or nicked DNA.
Replication Factories Disentangle Sister Chromatids. The disentanglement is essential for distributing the chromatids into daughter cells after DNA replication. Because sister chromatids after DNA replication hold each other by Cohesin rings, there is the only chance for the disentanglement in DNA replication. Fixing of replication machineries ...
The term plasmid was coined in 1952 by the American molecular biologist Joshua Lederberg to refer to "any extrachromosomal hereditary determinant." [11] [12] The term's early usage included any bacterial genetic material that exists extrachromosomally for at least part of its replication cycle, but because that description includes bacterial viruses, the notion of plasmid was refined over time ...
Drawing showing the difference between a circular DNA chromosome (a plasmid) with a secondary helical twist only, and one containing an additional tertiary superhelical twist superimposed on the secondary helical winding. In nature, circular DNA is always isolated as a higher-order helix-upon-a-helix, known as a superhelix. In discussions of ...
Nick translation [1] (or head translation), developed in 1977 by Peter Rigby and Paul Berg, is a tagging technique in molecular biology in which DNA polymerase I is used to replace some of the nucleotides of a DNA sequence with their labeled analogues, creating a tagged DNA sequence which can be used as a probe in fluorescent in situ hybridization (FISH) or blotting techniques.