DNA Replication Mechanism Quiz

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Questions and Answers

What is the primary function of DNA replication?

To transmit genetic information from cell to cell (correct)

To break down nucleotides for energy

To synthesize proteins from the DNA template

To create mutations in the genetic material

During which phase of the cell cycle does DNA replication occur in eukaryotes?

G1 phase

M phase

S phase (correct)

G2 phase

Which model of DNA replication proposes that both parental strands are conserved after replication?

Hybrid model

Dispersive model

Semiconservative model

Conservative model (correct)

What is the replication rate of nucleotides per minute in humans?

3,000 nucleotides Signup and view all the answers

What rule dictates the pairing of nucleotides during DNA replication?

AT/GC rule Signup and view all the answers

Which statement best describes the semiconservative model of DNA replication?

Half of the parental DNA is retained in each new double helix. Signup and view all the answers

Why is extreme accuracy crucial during DNA replication?

To preserve the integrity of the genome. Signup and view all the answers

Which of the following best describes the role of individual nucleotides during DNA replication?

They pair with nucleotides on template strands via hydrogen bonding. Signup and view all the answers

What is the role of helicase in DNA replication?

Unwind the DNA double helix Signup and view all the answers

In which direction is new DNA synthesized during replication?

5´-3´ direction only Signup and view all the answers

Which proteins are responsible for preventing premature reannealing of DNA during replication?

Single-strand binding proteins Signup and view all the answers

What initiates the synthesis of RNA primers in DNA replication?

RNA primase Signup and view all the answers

How does the lagging strand differ from the leading strand during DNA replication?

It is synthesized in fragments Signup and view all the answers

What is the function of topoisomerase during DNA replication?

Relieve torsional strain caused by unwinding Signup and view all the answers

What is formed when DNA replication is terminated?

Replication complex is released Signup and view all the answers

Which of the following statements is true regarding the origin of replication?

In eukaryotes, there are multiple sites of origin Signup and view all the answers

What function does the enzyme Ligase serve in DNA replication?

It binds Okazaki fragments together. Signup and view all the answers

Which property is true of all DNA polymerases?

They only add nucleotides to the 3´ end of existing strands. Signup and view all the answers

What is the primary role of DNA Pol I in bacteria?

Repair of DNA. Signup and view all the answers

What mechanism allows DNA polymerases to correct errors during DNA synthesis?

3 to 5 exonuclease activity. Signup and view all the answers

How does telomerase help in eukaryotic DNA replication?

It elongates the end of the lagging strand. Signup and view all the answers

Which statement best describes the error rate of DNA synthesis after proofreading?

1 in 1 billion base pairing errors. Signup and view all the answers

What occurs at the termination sites during prokaryotic DNA replication?

Replication forks meet and complete synthesis. Signup and view all the answers

What is the function of replication bubbles in DNA replication?

To enable simultaneous replication in both directions. Signup and view all the answers

Study Notes

DNA Replication

The process of copying the entire genome prior to cell division
Ensures the integrity of the genome across generations
Occurs during the S phase of the cell cycle in eukaryotes
Slower replication rate in eukaryotes results in higher fidelity/accuracy
Humans add 3000 nucleotides per minute; bacteria add 30,000 per minute
Relies on the complementarity of DNA strands, following the AT/GC rule

Mechanism of DNA Replication

Initiation:
- Initiator proteins bind to specific base sequences on DNA called "sites of origin"
- Prokaryotes have a single origin site (e.g., oriC in E. coli)
- Eukaryotes have multiple sites of origin (e.g., ARS sequences in yeast)
- Helicase unwinds and separates the double-stranded DNA, creating a replication fork
- Single-Strand Binding Proteins stabilize the separated strands
- Topoisomerase relieves stress on the DNA molecule during separation
Elongation:
- Synthesis always occurs in the 5´-3´ direction
- RNA primers are required to initiate nucleotide addition
- Primase synthesizes the RNA primer
- DNA polymerase adds nucleotides to the 3´ end of the primer
- Leading strand is synthesized continuously
- Lagging strand is synthesized discontinuously in short segments called Okazaki fragments
- Okazaki fragments are ~1000-2000 bp in prokaryotes and ~100-200 bp in eukaryotes
- DNA ligase joins the Okazaki fragments together
Termination:
- In prokaryotes, replication forks reach specific "termination sites"
- In eukaryotes, telomerase solves the problem of gaps left after RNA primer removal at the 5´ end of the lagging strand

Proteins Involved in DNA Replication

DNA polymerase: Adds nucleotides to the growing DNA strand. Proofreads for errors.
Helicase: Unwinds the DNA double helix
Topoisomerase: Relieves torsional stress from unwinding
RNA primase: Synthesizes RNA primers
Single-strand binding proteins: Prevents reannealing of separated DNA strands
DNA ligase: Joins Okazaki fragments on the lagging strand

Characteristics of DNA Polymerase

Synthesizes DNA in only one direction (5´-3´)
Requires a pre-existing double-stranded DNA to begin synthesis
Cannot initiate DNA synthesis from scratch

Proofreading and Error Correction

DNA polymerase initially makes errors at a rate of 1 in 10,000 base pairings
Proofreading enzymes correct these errors
DNA polymerases possess 3´-5´ exonuclease activity, allowing them to remove mismatched nucleotides
This process improves accuracy to 1 in 1 billion base pairing errors

Replication Bubbles

Replication occurs in both directions along the DNA
Both strands are replicated simultaneously
This process generates replication bubbles

Telomeres

Telomerase extends the lagging strand's 5´ end, preventing degradation
This solves the problem of gaps left after RNA primer removal
Essential in eukaryotes for maintaining chromosome stability

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Description

Test your knowledge on the DNA replication process, including the mechanisms involved in both prokaryotes and eukaryotes. This quiz covers initiation, elongation, and the importance of accuracy during replication. Understand the roles of various proteins and nucleotide pairing rules in maintaining genomic integrity.