The sliding clamp is a ring-shaped
protein that encircles duplex DNA, binds to the DNA polymerase and tethers it to the DNA template, preventing its dissociation and providing high processivity
.
What is the function of clamp loader?
Clamp loaders are members of the AAA+ family of ATPases and
use energy from ATP binding and hydrolysis to catalyze the mechanical reaction of loading clamps onto DNA
. Many structural and functional features of clamps and clamp loaders are conserved across all domains of life.
What is the function of the sliding clamp in DNA replication quizlet?
What is the role of the sliding clamp during replication?
It keeps DNA polymerase attached to the template while the polymerase synthesizes a new strand of DNA
. In the absence of the sliding clamp, most DNA polymerase molecules would synthesize only a short segment of DNA before falling off the template strand.
How does the B clamp processivity factor achieve its role during DNA replication?
β-clamp is loaded on the DNA, by clamp loader, a subunit of DNA Pol III. It interacts with several proteins other than DNA polymerase III subunits; it also freely slides along DNA and
improves the processivity of other proteins
.
Is the sliding clamp on the leading or lagging strand?
A DNA polymerase held to DNA by a mobile sliding clamp is nicely suited to highly processive synthesis on the
leading strand
of the replication fork but stands in contrast to the actions required on the lagging strand, which is synthesized as a series of Okazaki fragments in the direction opposite fork progression.
Why is the error rate for bacterial DNA replication very low quizlet?
Terms in this set (42) Why is it important for DNA replication to have a low error rate? DNA stores the information for products essential for life. With low fidelity
replication, the products necessary to sustain life would not be encoded for properly which would cause serious problems for survival
.
What are the 5 enzymes involved in DNA replication?
The enzymes involved in the replication of prokaryotic DNA are
DNA polymerase I to III, helicase, ligase, primase, sliding clamp, topoisomerase, and single-strand binding proteins (SSBs)
.
Which subunit is present in only one copy per DNA polymerase III?
The DNA polymerase III holoenzyme is a highly asymmetric structure due to the presence of only one copy of each of several subunits
(δ, δ′, χ, ψ)
in the clamp loader.
How would a nonfunctional clamp loader affect DNA replication?
It does not break any bonds. Which result would be a consequence of having a nonfunctioning clamp loader in a DNA replication reaction?
The polymerase would bind to the wrong area of the DNA. Primers would not be formed
.
Why is it necessary to have an RNA primer?
In living organisms, primers are short strands of RNA. … The synthesis of a primer is necessary
because the enzymes that synthesize DNA, which are called DNA polymerases, can only attach new DNA nucleotides to an existing strand of nucleotides
. The primer therefore serves to prime and lay a foundation for DNA synthesis.
What is the function of the Primase?
Primase functions by
synthesizing short RNA sequences that are complementary to a single-stranded piece of DNA
, which serves as its template. It is critical that primers are synthesized by primase before DNA replication can occur.
What enzyme removes primers?
Because of its 5′ to 3′ exonuclease activity,
DNA polymerase I
removes RNA primers and fills the gaps between Okazaki fragments with DNA.
Why is there a problem replicating the ends of linear DNA?
Unlike bacterial chromosomes,
the chromosomes of eukaryotes are linear
(rod-shaped), meaning that they have ends. These ends pose a problem for DNA replication. The DNA at the very end of the chromosome cannot be fully copied in each round of replication, resulting in a slow, gradual shortening of the chromosome.
What is the sliding clamp loader?
Clamp loaders are
pentameric ATPases of the AAA+ family
that operate to ensure processive DNA replication. They do so by loading onto DNA the ring-shaped sliding clamps that tether the polymerase to the DNA.
What prevents the DNA strands from sticking together after unwinding?
ATP is required to use ligase. Topo II enzymes cut both strands of DNA the molecule, untwist a portion through the cut, and reseal the cut. This introduces
negative supercoils
to help prevent the DNA from getting tangled up as it is unwound during replication and allow to be initated properly.
How are both the leading and the lagging strand synthesized at the same time?
The holoenzyme
synthesizes the leading and lagging strands simultaneously at the replication fork (Figure 27.32). … The leading strand is synthesized continuously by polymerase III, which does not release the template until replication has been completed.
