DNA Replication Quiz

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Questions and Answers

What is the name of the short, double-stranded region with a free OH group on the 3' end of the short strand, which is required for DNA polymerase to initiate synthesis?

Leading Strand

Okazaki Fragment

Lagging Strand

Primer (correct)

What is the name of the enzyme that catalyzes DNA chain elongation during replication?

RNA Polymerase

DNA Helicase

Ligase

DNA Polymerase III (correct)

Which of the following statements is TRUE about the lagging strand?

It is always longer than the leading strand.

It is synthesized discontinuously in the direction away from the replication fork. (correct)

It is synthesized using only one primer.

It is synthesized continuously in the direction of the replication fork.

Why is the leading strand synthesized continuously while the lagging strand is synthesized discontinuously?

The leading strand is synthesized in the direction of the replication fork, while the lagging strand is synthesized in the opposite direction. (C) Signup and view all the answers

Which of the following describes the role of helix destabilizing proteins (HD proteins) in DNA replication?

They unwind the DNA helix ahead of the replication fork. (C) Signup and view all the answers

What is the role of DNA helicase in DNA replication?

To unwind the DNA double helix. (B) Signup and view all the answers

How does the binding of HD proteins to single-stranded DNA shift the equilibrium towards single-stranded DNA?

They destabilize the double-stranded DNA structure, making it easier to separate. (A) Signup and view all the answers

Why is it necessary for DNA replication to be bidirectional?

To ensure that both strands of DNA are replicated simultaneously and efficiently. (A) Signup and view all the answers

In what direction does the new DNA strand grow during DNA replication?

5' to 3' (D) Signup and view all the answers

What is the function of the free 3' OH group of the primer in DNA replication?

It provides a starting point for DNA polymerase to add nucleotides. (D) Signup and view all the answers

What is the role of the origin of replication (Ori) in the initiation of DNA replication?

It provides a starting point for the unwinding of the DNA helix. (D) Signup and view all the answers

How do HD proteins facilitate the separation of parental DNA strands during replication?

They bind to the single strands of DNA and prevent them from re-annealing. (B) Signup and view all the answers

What is the role of the deoxyribonucleoside triphosphates (dATP, dTTP, dCTP, and dGTP) in DNA replication?

They provide the building blocks for the new DNA strand. (C) Signup and view all the answers

Which of the following statements about HD proteins is NOT true?

They act as enzymes to unwind the DNA helix. (A) Signup and view all the answers

In eukaryotes, how does the presence of multiple origins of replication contribute to the replication process?

It allows for faster replication of the larger eukaryotic genome. (A) Signup and view all the answers

How does the movement of the replication fork along the DNA contribute to the replication process?

It allows for the creation of two new daughter DNA molecules. (D) Signup and view all the answers

Which of the following is NOT a characteristic of DNA helicases?

They can reversibly cut a single strand of the double helix. (B) Signup and view all the answers

What is the primary role of Type I DNA Topoisomerases?

To relieve accumulated super-twists in the DNA helix by creating a transient nick. (C) Signup and view all the answers

What is the main difference between Type I and Type II DNA topoisomerases?

Type I topoisomerases create a nick in one strand of DNA while Type II create a nick in both strands. (B) Signup and view all the answers

Which enzyme is responsible for synthesizing the new DNA strand in the 5' → 3' direction?

DNA polymerase III (D) Signup and view all the answers

What is the role of primase in DNA replication?

To synthesize short RNA primers that provide a starting point for DNA polymerase. (B) Signup and view all the answers

Why is the lagging strand synthesized discontinuously in Okazaki fragments?

Because DNA polymerase can only add nucleotides to the 3' end of a growing strand. (C) Signup and view all the answers

What is the function of SSB proteins in DNA replication?

To prevent the separated strands of DNA from re-annealing. (C) Signup and view all the answers

Which of the following enzymes is NOT involved in DNA replication?

RNA polymerase II (C) Signup and view all the answers

What is the main purpose of 3'→5' exonuclease activity in DNA polymerase III?

To remove incorrectly paired nucleotides from the newly synthesized strand. (A) Signup and view all the answers

Which of the following is NOT a consequence of errors in DNA replication?

Increased rate of cell division. (C) Signup and view all the answers

What is the role of nucleotide analogues in DNA replication?

They can block DNA chain growth, inhibiting cell division. (C) Signup and view all the answers

Why is it crucial for DNA polymerase III to have both 5'→3' polymerase activity and 3'→5' exonuclease activity?

To ensure that the new DNA strand is complementary to the template strand. (C) Signup and view all the answers

What is the significance of DNA polymerase III's ability to hydrolytically remove mismatched nucleotides?

It prevents the accumulation of errors in the newly synthesized DNA strand. (C) Signup and view all the answers

Which of the following statements accurately describes the difference between the leading and lagging strands in DNA replication?

The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously. (A) Signup and view all the answers

What is the primary function of the HD Protein Helicase in DNA replication?

To unwind the DNA helix and separate the strands. (D) Signup and view all the answers

What is the role of the template strand in DNA replication?

It acts as a guide for the synthesis of the new DNA strand. (D) Signup and view all the answers

What activity allows DNA polymerase I to remove RNA primers during DNA synthesis?

5’→3’ exonuclease activity (A) Signup and view all the answers

Which activity of DNA polymerase III is crucial for proofreading newly synthesized DNA?

3’→5’ exonuclease activity (D) Signup and view all the answers

What is the primary function of DNA polymerase I in the context of RNA primers?

Remove RNA primers and replace with DNA (A) Signup and view all the answers

Which direction does DNA polymerase I synthesize DNA?

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

What sequence of events occurs when DNA polymerase III encounters an RNA primer?

It excises the RNA primer and stops synthesis. (B) Signup and view all the answers

What type of nucleotides does DNA polymerase I use to fill the gap left after removing RNA primers?

Deoxyribonucleotides (D) Signup and view all the answers

In the context of DNA synthesis, what is the role of the 3’→5’ exonuclease activity?

To degrade mismatched or improperly paired nucleotides (C) Signup and view all the answers

Which enzyme is responsible for continuing DNA synthesis until blocked by an RNA primer?

DNA polymerase III (C) Signup and view all the answers

What is the primary function of 5'→3' exonuclease activity of DNA polymerase I?

It removes nucleotides from a properly base paired region of DNA. (D) Signup and view all the answers

What role does DNA ligase play in the DNA replication process?

It catalyzes the linkage between DNA chains synthesized by different polymerases. (A) Signup and view all the answers

Which statement accurately describes the activity of DNA polymerase β (Beta)?

It participates in editing and repair of DNA. (A) Signup and view all the answers

The process of removing mismatched ends during DNA replication is primarily attributed to which activity?

5'→3' exonuclease activity of DNA polymerase I (C) Signup and view all the answers

Which statement is true regarding the energy requirements for DNA replication in humans?

ATP is broken down to AMP and PPi to provide energy. (D) Signup and view all the answers

What is the unique function of DNA polymerase Υ (Upsilon)?

It is involved in mitochondrial DNA synthesis. (B) Signup and view all the answers

What differentiates the activity of the 5'→3' exonuclease from the 3'→5' exonuclease in DNA polymerases?

5'→3' removes nucleotides while 3'→5' edits and proofreads. (D) Signup and view all the answers

Which of the following describes the consequence of RNA degradation during DNA synthesis?

It enables gaps to be filled with DNA after RNA removal. (B) Signup and view all the answers

Study Notes

DNA and RNA Structure

DNA is a double helix, with antiparallel strands
Nucleotides are linked by phosphodiester bonds
A pairs with T, and G pairs with C (base pairing)
DNA strands have a 5' and 3' end
Hydrogen bonding holds base pairs together (A-T, G-C)
The distance between DNA base pairs is 0.34nm
RNA is single-stranded, and not a double helix
Nucleotides are also linked by phosphodiester bonds
A pairs with U, and G pairs with C (base pairing)
Different types of RNA exist, including mRNA, tRNA, rRNA

Erwin Chargaff's Rules

Chargaff's rules describe the consistent ratios of nitrogenous bases in DNA.
Rule #1: Guanine always pairs with cytosine, and adenine always pairs with thymine. These pairings occur in equal percentages
Rule #2: The proportions of DNA bases vary between species, although equal percentages of guanine + cytosine, and adenine + thymine hold true.

DNA Replication

DNA replication is semi-conservative
The two strands of DNA separate, and each serves as a template to synthesize a new complementary strand
Enzymes are involved in unwinding DNA(helicases), providing stabilization for the unwound DNA strands(SSB proteins) separating the single stranded DNA strands (DNA topoisomerases), adding nucleotides to the growing strands (DNA polymerases) and connecting the Okazaki fragments (DNA ligases).
Several different DNA polymerases are involved in replication, with differing functions in the process
Multiple origins of replication occur in eukaryotes, as opposed to a single origin of replication in prokaryotes.

RNA Polymerase, Transcription and translation

RNA polymerase synthesizes RNA from DNA
mRNA carries genetic information from DNA to ribosomes
rRNA is a component of ribosomes
tRNA transfers amino acids to the ribosome during protein synthesis

Other Important Figures and Concepts

Oswald Avery: His work was important to identify DNA as a transforming factor
Photo 51: A key X-ray diffraction image that helped determine the structure of DNA

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Description

Test your knowledge on the essential processes of DNA replication, including roles of enzymes and the structure of DNA strands. This quiz covers concepts such as leading and lagging strands, the function of helicase, and the mechanism of initiation at the origin of replication. Perfect for biology students looking to reinforce their understanding of molecular genetics.