DNA Replication Proteins: Helicases and Single-Strand Binding Proteins

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What is the function of DNA helicases in DNA replication?

To synthesize new DNA strands
To bind tightly to single-stranded DNA
To catalyze the formation of short hairpin helices
To unwind the DNA double helix in front of the replication fork (correct)

In what direction can a DNA helicase unwind the DNA double helix?

In either the 5′-to-3′ or 3′-to-5′ direction (correct)
Only in the 5′-to-3′ direction
Only in the 3′-to-5′ direction
In a random direction

What is the role of single-strand DNA-binding proteins (SSB) in DNA replication?

To synthesize new DNA strands
To unwind the DNA double helix
To catalyze the formation of short hairpin helices
To bind tightly to single-stranded DNA and prevent hairpin helix formation (correct)

What is the consequence of not removing short hairpin helices on the lagging strand template?

DNA synthesis is impeded (B) Signup and view all the answers

What is the characteristic of DNA polymerase molecules during DNA synthesis?

They synthesize only a short string of nucleotides before falling off (A) Signup and view all the answers

What is the speed of DNA helicase movement along a single DNA strand?

Up to 1000 nucleotides per second (A) Signup and view all the answers

What is the energy source for DNA helicase activity?

ATP hydrolysis (A) Signup and view all the answers

What is the result of DNA helicase binding to single strands of DNA?

The change in shape of the protein molecule (D) Signup and view all the answers

What is the primary function of DNA polymerase during DNA replication?

To proofread and correct initial mispairings (D) Signup and view all the answers

What is the purpose of the conformational change in DNA polymerase during DNA replication?

To enable the polymerase to 'double-check' the base pair geometry (A) Signup and view all the answers

What is the result of the accidental incorporation of ribonucleotides during DNA replication?

The correction of replication errors (C) Signup and view all the answers

What is the role of DNA topoisomerases during DNA replication?

To prevent DNA tangling (A) Signup and view all the answers

What is the characteristic of the DNA replication fork?

It is asymmetrical (A) Signup and view all the answers

What is the purpose of the strand-directed mismatch repair system?

To remove replication errors (B) Signup and view all the answers

What is the outcome of the high fidelity of DNA replication?

The accurate transmission of genetic information (D) Signup and view all the answers

What is the primary mechanism that ensures the high fidelity of DNA replication?

The proofreading mechanisms (C) Signup and view all the answers

What is the primary function of the PCNA protein in eukaryotes during DNA replication?

To form a sliding clamp that keeps the polymerase firmly on the DNA (B) Signup and view all the answers

How does the DNA polymerase on the lagging-strand template interact with the clamp during DNA replication?

It releases itself from the clamp and dissociates from the template at the 5′ end of each Okazaki fragment (B) Signup and view all the answers

What is the role of the clamp loader in the assembly of the clamp around the DNA?

To open and close the ring in a regulated manner (B) Signup and view all the answers

What is the characteristic of the interaction between the DNA polymerase and the clamp on the leading strand?

The polymerase is tightly bound to the clamp and remains associated for a very long time (B) Signup and view all the answers

What is the purpose of the clamp in DNA replication?

To keep the polymerase firmly on the DNA during replication (B) Signup and view all the answers

What is the consequence of the DNA polymerase reaching the 5′ end of the preceding Okazaki fragment on the lagging strand?

The polymerase releases itself from the clamp and dissociates from the template (C) Signup and view all the answers

What is the function of the clamp loader in the context of the lagging-strand polymerase?

To load a new clamp onto the RNA primer of the next Okazaki fragment (D) Signup and view all the answers

What is the structural characteristic of the clamp protein that allows it to slide freely along the DNA?

It forms a large ring around the DNA double helix (B) Signup and view all the answers

What is the role of 3’ to 5’ proofreading exonuclease in DNA polymerase?

To remove incorrect nucleotides from the primer strand (A) Signup and view all the answers

Why is DNA polymerase unable to start DNA synthesis de novo?

Because it requires an existing primer (A) Signup and view all the answers

What is the direction of DNA replication that allows for efficient error correction?

5’ to 3’ (A) Signup and view all the answers

What is the function of special proteins during DNA replication?

To open up the DNA double helix in front of the replication fork (C) Signup and view all the answers

What is the characteristic of the DNA double helix under physiological conditions?

It is very stable and requires high temperatures to separate (A) Signup and view all the answers

What is the role of exonucleolytic proofreading during DNA replication?

To correct errors during DNA synthesis (C) Signup and view all the answers

What is the characteristic of DNA polymerase?

It is a self-correcting enzyme that removes its own polymerization errors (A) Signup and view all the answers

What is synthesized by a special nucleotide-polymerizing enzyme?

Short RNA primer molecules (C) Signup and view all the answers

What is the approximate rate of mutation in DNA replication?

One nucleotide change per 10^10 nucleotides (D) Signup and view all the answers

Why is it necessary to maintain low mutation rates in DNA replication?

To maintain the organized structure of the body (D) Signup and view all the answers

What is the significance of maintaining accurate genetic instructions in DNA replication?

To pass accurate genetic instructions from one generation to the next (D) Signup and view all the answers

Which type of cells must be protected against high rates of mutation?

Germ cells (C) Signup and view all the answers

What is the consequence of high mutation rates in somatic cells?

Cancer (B) Signup and view all the answers

What is the approximate size of the human genome?

3.1 X 10^9 nucleotide pairs (B) Signup and view all the answers

Why is high fidelity in DNA replication necessary?

To maintain life as we know it (D) Signup and view all the answers

What is the result of maintaining accurate genetic instructions in DNA replication?

Accurate genetic instructions from one generation to the next (C) Signup and view all the answers