OD 515 DNA Replication- Questions Exam 1 with
complete solutions.
Semi-conservative replication
Mechanism where each original DNA strand serves as a template for a new complementary
strand.
Direction of DNA synthesis
5' to 3' direction only.
Why do DNA polymerases require RNA primers?
They cannot initiate synthesis de novo and require a pre-existing 3'-OH group.
Primase
The enzyme that synthesizes RNA primers required for DNA replication.
Leading vs. lagging strand synthesis
Leading strand is synthesized continuously; lagging strand is synthesized discontinuously in
Okazaki fragments.
Pre-Replicative Complex (pre-RC) assembly phase
Assembles during the G1 phase of the cell cycle.
Pre-RC components
Origin Recognition Complex (ORC), Cdc6, Cdt1, and MCM2-7 helicase.
CMG complex
, The active replicative helicase in eukaryotes composed of Cdc45, MCM2-7, and GINS.
Replication Protein A (RPA)
Binds single-stranded DNA to prevent re-annealing and protect it from nuclease degradation.
Topoisomerase I vs. Topoisomerase II mechanism
Topoisomerase I makes single-strand breaks (no ATP); Topoisomerase II makes double-strand
breaks (requires ATP).
PCNA (Proliferating Cell Nuclear Antigen)
A ring-shaped sliding clamp that acts as a processivity factor for DNA polymerases.
Replication Factor C (RFC)
The clamp loader that uses ATP to load PCNA onto DNA.
DNA Polymerase α (Pol α)
Works with primase to synthesize initial RNA-DNA primers; lacks proofreading.
DNA Polymerase ε (Pol ε)
The primary polymerase responsible for leading strand synthesis in eukaryotes.
DNA Polymerase δ (Pol δ)
The primary polymerase responsible for lagging strand synthesis in eukaryotes.
Eukaryotic primer removal enzymes
RNase H1 removes RNA; FEN1 cleaves the remaining DNA flap.
DNA Ligase I
complete solutions.
Semi-conservative replication
Mechanism where each original DNA strand serves as a template for a new complementary
strand.
Direction of DNA synthesis
5' to 3' direction only.
Why do DNA polymerases require RNA primers?
They cannot initiate synthesis de novo and require a pre-existing 3'-OH group.
Primase
The enzyme that synthesizes RNA primers required for DNA replication.
Leading vs. lagging strand synthesis
Leading strand is synthesized continuously; lagging strand is synthesized discontinuously in
Okazaki fragments.
Pre-Replicative Complex (pre-RC) assembly phase
Assembles during the G1 phase of the cell cycle.
Pre-RC components
Origin Recognition Complex (ORC), Cdc6, Cdt1, and MCM2-7 helicase.
CMG complex
, The active replicative helicase in eukaryotes composed of Cdc45, MCM2-7, and GINS.
Replication Protein A (RPA)
Binds single-stranded DNA to prevent re-annealing and protect it from nuclease degradation.
Topoisomerase I vs. Topoisomerase II mechanism
Topoisomerase I makes single-strand breaks (no ATP); Topoisomerase II makes double-strand
breaks (requires ATP).
PCNA (Proliferating Cell Nuclear Antigen)
A ring-shaped sliding clamp that acts as a processivity factor for DNA polymerases.
Replication Factor C (RFC)
The clamp loader that uses ATP to load PCNA onto DNA.
DNA Polymerase α (Pol α)
Works with primase to synthesize initial RNA-DNA primers; lacks proofreading.
DNA Polymerase ε (Pol ε)
The primary polymerase responsible for leading strand synthesis in eukaryotes.
DNA Polymerase δ (Pol δ)
The primary polymerase responsible for lagging strand synthesis in eukaryotes.
Eukaryotic primer removal enzymes
RNase H1 removes RNA; FEN1 cleaves the remaining DNA flap.
DNA Ligase I
