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Upon helicase activity on the duplex, the quencher and lanthanide labels get separated as the DNA is unwound. This loss in proximity negates the quenchers ability to repress the lanthanide signal, causing a detectable increase in fluorescence that is representative of the amount of unwound DNA and can be used as a quantifiable measurement of ...
The DNA helicase and associated enzymes are now able to bind to the unwound region, creating a replication fork start. The unwinding of this duplex strand region is associated with a low free energy requirement, due to helical instability caused by specific base-stacking interactions, in combination with counteracting supercoiling.
DNA replication: The double helix is 'unzipped' and unwound, ... the Mcm complex is the helicase that will split the DNA helix at the replication forks and origins ...
Consider the following: the helicase continuously unwinds the parental duplex, but the lagging strand must be polymerised in the opposite direction. This means that, while polymerisation of the leading strand proceeds, polymerisation of the lagging strand only occurs after enough of the lagging strand has been unwound by the helicase.
After the replicative helicase has unwound the parental DNA duplex, exposing two single-stranded DNA templates, replicative polymerases are needed to generate two copies of the parental genome. DNA polymerase function is highly specialized and accomplish replication on specific templates and in narrow localizations.
DNA gyrase, or simply gyrase, is an enzyme within the class of topoisomerase and is a subclass of Type II topoisomerases [1] that reduces topological strain in an ATP dependent manner while double-stranded DNA is being unwound by elongating RNA-polymerase [2] or by helicase in front of the progressing replication fork.
As the DNA double helix is unwound by helicase, replication occurs separately on each template strand in antiparallel directions. This process is known as semi-conservative replication because two copies of the original DNA molecule are produced, each copy conserving (replicating) the information from one half of the original DNA molecule.
Insights into initiation complex architecture will help explain not only how origin DNA is melted, but also how a replicative helicase is loaded directionally onto each of the exposed single DNA strands in the unwound DUE, and how these events are aided by interactions of the helicase with the initiator and specific loader proteins. [2]