DNA Replication Quiz

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Questions and Answers

What is the primary role of DNA primase in DNA synthesis?

To stabilize the DNA double helix during synthesis

To add RNA primers to initiate DNA polymerization (correct)

To generate energy for the polymerization process

To remove errors introduced during DNA synthesis

Why can't DNA polymerase start polymerizing DNA directly?

It requires a DNA template strand first

It requires multiple RNA primers initially

It needs a free 3'OH group added by primase (correct)

It cannot recognize incoming nucleotides

What is the primary function of DNA polymerase I?

Elongates the leading strand

Substitutes for DNA polymerase II

Synthesizes RNA primers

Fills in small DNA segments during repair or replication (correct)

What happens to RNA primers after DNA synthesis is complete?

They are removed and replaced with DNA Signup and view all the answers

Which DNA polymerase is responsible for synthesizing the lagging strand in eukaryotes?

DNA polymerase δ Signup and view all the answers

What is one limitation of DNA primase during DNA synthesis?

It lacks a self-correcting mechanism Signup and view all the answers

How does DNA polymerase ensure correct base pairing during DNA synthesis?

By releasing energy from the hydrolysis of pyrophosphate Signup and view all the answers

What role does the sliding clamp protein play in DNA replication?

It increases the processivity of DNA polymerase III Signup and view all the answers

How does DNA polymerase correct errors made during DNA replication?

By using a 3’-5’ exonuclease activity Signup and view all the answers

Which statement about prokaryotic DNA replication is accurate?

The catalytic core of DNA polymerase III synthesizes multiple daughter strands simultaneously. Signup and view all the answers

What forms the backbone of a DNA strand?

Nucleotides linked by phosphodiester bonds Signup and view all the answers

Which enzyme is responsible for synthesizing RNA primers during DNA replication?

DNA Primase Signup and view all the answers

What is the function of topoisomerase in DNA replication?

To eliminate topological links and facilitate unwinding Signup and view all the answers

Why is DNA replication considered semiconservative?

Each new DNA molecule contains one old strand and one new strand Signup and view all the answers

What is unique about the lagging strand during DNA replication?

It is synthesized in fragments and not continuously Signup and view all the answers

What type of exonuclease activity does DNA Pol III possess?

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

What error rate does DNA replication achieve due to proofreading mechanisms?

1 in every 1 billion base pairs Signup and view all the answers

What occurs immediately after an incorrect nucleotide is incorporated during DNA replication?

Exonucleolytic proofreading occurs Signup and view all the answers

Which of the following statements is true regarding strand-directed mismatch repair?

It identifies and repairs distortions due to non-complementary bases. Signup and view all the answers

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

To correct mismatched nucleotides at the primer terminus Signup and view all the answers

Study Notes

DNA Replication

DNA replication is a semi-conservative process, producing two identical DNA molecules from one original DNA molecule.
Each new DNA molecule consists of one original strand and one new strand.
The process begins with the unwinding of the DNA double helix, creating a replication fork.
DNA helicases are responsible for disrupting hydrogen bonds to separate DNA strands.
Topoisomerases remove topological links between the two strands, facilitating unwinding.
DNA primase synthesizes short RNA primers to initiate DNA replication.
DNA polymerase synthesizes new DNA strands complementary to the template strand.
DNA polymerase III is the main enzyme for DNA replication, moves 5' to 3'.
Okazaki fragments are short DNA fragments formed on the lagging strand in the 5' to 3' direction.
DNA ligase joins Okazaki fragments together to create a continuous lagging strand.
DNA replication occurs in both directions in prokaryotes and eukaryotes.
DNA replication has specific origins in eukaryotes and prokaryotes.
DNA polymerase I is mainly involved in filling gaps and removing RNA primers during repair.
The initiation of DNA replication is dependent on pre-replicative complexes.
DNA helicases use ATP for propulsion along a DNA single strand to separate the double helix.
Single-strand DNA-binding proteins bind to single-stranded DNA behind helicase, preventing the DNA strands from reforming double strands.
Topoisomerase I produces a transient single-strand break in the DNA phosphodiester backbone to relieve the tension.
DNA polymerase has 3' to 5' exonuclease activity for error correction and proofreading as it goes.
DNA polymerase also has 5' to 3' exonuclease activity to remove RNA primer.
Mismatch repair systems are used to correct errors in newly synthesized DNA.
DNA polymerase error rate is approximately 1 in 100,000 base pairs, but the cell can correct these mistakes.
There are many enzymes involved in DNA replication and repair, each with specific functions.

DNA Repair

DNA repair mechanisms are vital for maintaining the integrity of the genome.
DNA repair systems can be classified into different pathways based on the types of damage.
Several different types of DNA damage can occur.
DNA repair mechanisms are important for correcting damage to the DNA structure.
Multiple pathways exist to address various types of DNA damage.
The high fidelity of replication is attributed to the initial base pairing and several “proofreading” mechanisms.
DNA repair can be further categorized as direct reversal of DNA damage, base excision repair (BER), nucleotide excision repair (NER), mismatch repair, homologous recombination (HR), and non-homologous end joining (NHEJ).

Types of DNA Damage and Repair

Depurination: Loss of a purine base (guanine or adenine) from DNA.
Deamination: Conversion of a cytosine to uracil, or an adenine to hypoxanthine.
Base Dimerization: Covalent linkage of adjacent thymine or cytosine bases, due to UV radiation.

Additional Information

Specific proteins and enzymes are involved in each DNA repair pathway.
Defects in DNA repair pathways can lead to various genetic diseases and an increased risk of cancer.

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Description

Test your knowledge on the key enzymes and processes involved in DNA replication. This quiz covers various aspects, including the functions of DNA primase, polymerases, and the role of RNA primers. Dive into the intricacies of replication in both prokaryotic and eukaryotic systems.