DNA Replication: Start to FInish Flashcards
(50 cards)
What three major events can DNA replication be divided into?
- initiation
- elongation
- termination
Where does Ecoli start replication?
At a specific site in the DNA known as the oriC (origin of replication) which four 9mers having a consensus sequence of TTATCCACA.
What are the four 9mers binding site for?
dnaA gene product: DnaA
What is the function of DnaA?
It facilitates the binding of DnaB. It also stimulates the melting of the three 13mer repeats at one end of the oriC (italicized) to make an open complex.
WHat is the DnaB protein function?
It is required for primer synthesis it is the DNA helicase component of the primosome.
What other protein binds to DnaB and has the role of assisting it to reach oriC (italicized)?
DnaC
What other two factors in Ecoli are required to create an open complex at oriC (italicized)? And how do they help to form an open complex?
- RNA polymerase is required to synthesize a short piece of RNA that creates an R loop.
- HU protein (helix unwinding protein) that induces bending in the double stranded DNA.
The bending plus the R loop destabilize the dsDNA and facilitates melting of the DNA to form the open complex.
What is the primase and what is it made of?
It is the primer synthesizing enzyme and it is the product of the DnaG (italicized) gene and the RNA primer-synthesizing enzyme.
What s the primase also called?
DnaG
WHat is the primosome made of and what is its two functions?
DnaG and the DnaB protein.
It is responsible for laying down MULTIPLE OKAZAKI FRAGMENT PRIMERS on the lagging strand and serving as the helicase (DnaB component) that moves 5’—>3’ on the lagging strand in the direction of the replication fork.
Why does a more complicated system for DNA initiation exist in Eukaryotes?
Eukaryote genomes are much larger and the replication forks in eukaryotes moves at a slower rate.
How does the eukaryotic organism overcome the difficulties of its DNA replication?
It has MULTIPLE origins of replication for each chromosome.
Where is the origin of replication located in yeasts?
ARS (autonomously replicating sequences
WHat are the ARSs in yeasts composed of?
4 distinct and important regions and one of the regions is involved in allowing for the local DNA bending.
When can elongation commence in E coli?
WHen there is a primer present open DNA strand
The DNA Pol II holoenzyme is very processive. WHat attributes to this processivity?
The presence of a Sliding Clamp
What subunit of the holoenzyme and what is the function of the sliding clamp?
Beta subunit of the holoenzyme and it holds the entire Pol III assembly on the template for long periods of time.
What other complex does the Sliding Beta Clamp require to associate with the DNA?
It requires the activity of the Gamma Complex which is composed of other protein subunits. It serves as the clamp loader.
What os the clamp loader made of?
The gamma complex
Clamp loading is ________ dependent.
ATP
The Beta clamp is a dimer or trimer?
dimer
WHat is the processivity factor in Eukaryotes?
Proliferating cell nuclear antigen (PCNA)
What does PCNA form?
aA trimer that encircles the DNA as the Beta Clamp does.
Polyermerase II holoenzyme actually contains _____ core polymerases since _____ strand of DNA need to be replicated>
two
two
