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For DNA polymerases to function, the double-stranded DNA helix has to be unwound to expose two single-stranded DNA templates for replication. DNA helicases are responsible for unwinding the double-stranded DNA during chromosome replication. Helicases in eukaryotic cells are remarkably complex. [106]
Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes. Due to this problem, DNA is lost in each replication cycle from the end of the chromosome.
DNA is a duplex formed by two anti-parallel strands. Following Meselson-Stahl, the process of DNA replication is semi-conservative, whereby during replication the original DNA duplex is separated into two daughter strands (referred to as the leading and lagging strand templates). Each daughter strand becomes part of a new DNA duplex.
To change this template's initial visibility, the |state= parameter may be used: {{DNA replication | state = collapsed}} will show the template collapsed, i.e. hidden apart from its title bar. {{DNA replication | state = expanded}} will show the template expanded, i.e. fully visible.
DNA molecules in eukaryotes differ from the circular molecules of prokaryotes in that they are larger and usually have multiple origins of replication. This means that each eukaryotic chromosome is composed of many replicating units of DNA with multiple origins of replication. In comparison, prokaryotic DNA has only a single origin of ...
DNA replication also works by using a DNA template, the DNA double helix unwinds during replication, exposing unpaired bases for new nucleotides to hydrogen bond to. Gene synthesis, however, does not require a DNA template and genes are assembled de novo. DNA synthesis occurs in all eukaryotes and prokaryotes, as well as some viruses. The ...
Rolling circle replication (RCR) is a process of unidirectional nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA or RNA, such as plasmids, the genomes of bacteriophages, and the circular RNA genome of viroids. Some eukaryotic viruses also replicate their DNA or RNA via the rolling circle mechanism.
Because the binding of the polymerase to the template is the rate-limiting step in DNA synthesis [citation needed], the overall rate of DNA replication during S phase of the cell cycle is dependent on the processivity of the DNA polymerases performing the replication. DNA clamp proteins are integral components of the DNA replication machinery ...