Molecular Bio (Exam 1): DNA Replication

What enzyme is the replicase in E. coli?

DNA pol III.

Which enzymes are the error-prone polymerases in E. coli?

DNA pol IV, and V.

Which enzyme is the replicase in eukaryotes?

DNA pol δ, and ɛ.

Proofreading in DNA synthesis removes nucleotides in what direction?

3’-5’.

Proofreading in DNA synthesis is done by what enzyme activity of DNA polymerase?

exonuclease.

If wrong nucleotides are not corrected, what mutations may occur?

substitution.

Processivity refers to the ability of an enzyme to perform __________ catalytic cycles with a single template, instead of dissociating after each cycle.

multiple.

What does replication require to processively separate the strands of DNA using ATP?

helicase (DnaB or MCM).

Single-strand binding (SSB) proteins are crucial for what DNA synthesis?

lagging strand.

What is required to start DNA synthesis?

Priming.

DNA polymerases require what kind of end for DNA synthesis?

3’-OH priming end.

What is a molecule that provides a free 3’-OH end?

primer.

What are the 4 components of the DNA pol III holoenzyme complex in E. coli?

Core, clamp, clamp loader, and tau.

Why does the DNA pol III holoenzyme complex have 2 core enzymes?

One core enzyme is for leading strand synthesis; the other core enzyme is for lagging strand synthesis.

What are the 3 subunits that compose the core enzyme DNA pol III?

α, ε, θ.

What is the polymerase subunit in the DNA pol III core enzyme?

α.

What is the 3’-5’ exonuclease subunit in the DNA pol III core enzyme?

ε

What stimulates the exonuclease activity of the ε subunit in the DNA pol III core enzyme?

θ

What subcomplex in the DNA pol III holoenzyme is the processivity factor?

β clamp.

What complex in the DNA pol III holoenzyme is the clamp loader?

γ complex.

What process does the γ complex require to place the β clamp onto DNA?

ATP hydrolysis.

What complex in the DNA pol III holoenzyme links the 2 catalytic cores and binds to DnaB helicase?

tau.

What is the difference between the clamps on leading strands and the clamps on lagging strands?

Leading strand: binds once and stays until the end of replication.
Lagging strand: must dissociate and rebind with every Okazaki fragment.

What protein must interact with DnaG primase to initiate each Okazaki fragment?

DnaB helicase.

Which protein does DnaB helicase have to interact with to initiate each Okazaki fragment?

DnaG primase.

Which protein is responsible for forward movement at the replication fork?

DnaB helicase.

After Okazaki fragment is synthesized, what enzyme replaces RNA primer with DNA?

DNA pol I.

What activity does DNA pol I do?

5’-3’ exonuclease activity.

What synthesizes RNA primers in E. coli?

DnaG primase.

What synthesizes RNA primers in eukaryotes?

DNA pol α (primase).

What removes primers in E. coli?

DNA pol I.

What removes primers in eukaryotes?

RNase H, FEN1.

What DNA polymerases are required for eukaryotic DNA replication in the nucleus?

pol α/primase, pol ε, pol δ.

What enzyme complex initiates the synthesis of leading and lagging strands in eukaryotes?

DNA pol α complex (primase).

What enzyme elongates the leading strand in eukaryotes?

Pol ε.

What enzyme elongates the lagging strand in eukaryotes?

Pol δ.

When do the multiple replicons replicate in eukaryotic cell cycle?

different times throughout S phase.