chapter 11 Flashcards
The replication of DNA proceeds with one parental strand used as template to build a new double helix
that will include a parental molecule and a newly synthesized molecule
semiconservative
what direction is DNA Replication
Bidirectional
Once replication has started, the point where the DNA is separated into two strands, each of which is replicated,
is called
replication fork
where replication begins
origin of replication
are present to
replicate whole eukaryotic chromosomes
multiple origins of replication
All DNA polymerases synthesize a new DNA molecule with
direction
5’ to 3’
as only one strand is
synthesized continuously while the other is polymerized in pieces.
semidiscontinuous
strand that is synthesized continuously
leading strand
synthesized in pieces
lagging strand
DNA polymerases require a blank which guides the insertion of new nucleotides
template strand
required by DNA polymerases and are elongated
primer strand
as it is used to
remove mismatched nucleotides
proofreading with the 3’ to 5’ exonuclease
Dissociating completely from the DNA
strand after each insertion.
distributive synthesis
Sliding forward of one base pair to
reposition the 3’ terminus
processive synthesis
is a heterotrimer composed of
subunits α, ε, and θ.
Alpha: polymerase activity
Epsilon: proofreading 3’5’ activity
Theta: unknown role
Polymerase 3 core
is substantially larger
and includes three Pol III cores, two ring-shaped
β sliding clamps
Pol III holoenzyme
includes a series
of proteins that ultimately differentiate the
activity of the holoenzyme from that of the
single cores
Pol III holoenzyme
The β sliding clamp is a
homodimer
separate the two DNA strands via NTP hydrolysis (typically ATP hydrolysis). They bind to a single-
stranded gap in DNA and move along it “propelled” by ATP hydrolysis. As they move, they unwind DNA. They can move in either direction, depending on the type
helicases
The Pol III holoenzyme, DnaB and primase constitutes the
replisome
the action of a blank is required to reduce the superhelical tension
topoisomerase
it binds the DNA helicase for activity. RNA synthesis is less accurate than
DNA synthesis and this is how RNA primers are then recognized and digested
DNaG is the primase in E. coli
hat protects the single strand from nucleases. In E. coli, SSB is a tetramer but this quaternary structure changes in other organisms
single-stranded DNA–binding protein (SSB)
a helicase complex formed by 6
homologous but not identical subunits (named Mcm2 through Mcm7) with AAA+ activity (ATPase). Like DnaB,
this is a ring-shaped hexamer.
MCM complex
