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What is the role of DNA ligase during DNA replication?

  • Proofreads newly synthesized DNA.
  • Separates the DNA strands.
  • Initiates replication at the origin.
  • Joins 3’ dNT to 5’ end of Okazaki fragments. (correct)

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

  • G2 phase
  • G1 phase
  • S phase (correct)
  • M phase

    • What are replicons in the context of eukaryotic DNA replication?

  • The polymerases that synthesize DNA.
  • Proteins required for proofreading.
  • Single nucleosomes involved in coding.
  • Regions of DNA that replicate independently. (correct)

    • What is the main function of mismatch repair in prokaryotes?

    <p>To remove mispaired nucleotides from the growing DNA strand.</p> Signup and view all the answers

    Which statement about the incorporation of nucleotides during DNA replication is accurate?

    <p>Base pairs must maintain a specific geometric fit to be incorporated.</p> Signup and view all the answers

    What is the main purpose of DNA replication?

    <p>To copy genetic material for cell division</p> Signup and view all the answers

    What does the term 'semi-conservative replication' refer to?

    <p>Each daughter DNA molecule contains one parental and one new strand.</p> Signup and view all the answers

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

    <p>S Phase</p> Signup and view all the answers

    How many origins of replication can be found in human cells?

    <p>10,000-100,000</p> Signup and view all the answers

    What characterizes the replication forks during DNA replication?

    <p>They are sites of parental strand separation and incorporate nucleotides.</p> Signup and view all the answers

    How many replication foci are typically found in a replicating nucleus?

    <p>50-250</p> Signup and view all the answers

    What is the function of DNA Polymerase III during DNA replication?

    <p>To synthesize the daughter strands.</p> Signup and view all the answers

    What are replicons?

    <p>Small portions of the eukaryotic genome that are replicated.</p> Signup and view all the answers

    What is the main function of Type II topoisomerases?

    <p>To introduce or remove supercoils in DNA</p> Signup and view all the answers

    What enzyme is responsible for synthesizing RNA primers on the lagging strand during DNA replication in prokaryotes?

    <p>Primase</p> Signup and view all the answers

    Which component is NOT part of the DNA polymerase III holoenzyme?

    <p>Replisome</p> Signup and view all the answers

    What direction does DNA polymerase synthesize new DNA?

    <p>5' to 3'</p> Signup and view all the answers

    What initiates the unwinding of DNA in prokaryotes?

    <p>DnaB helicase</p> Signup and view all the answers

    What is the role of the helicase enzyme during DNA replication in prokaryotes?

    <p>To unwind DNA strands</p> Signup and view all the answers

    Which statement about DNA polymerase III is incorrect?

    <p>It requires ATP during replication.</p> Signup and view all the answers

    Which enzyme replaces RNA primers with DNA during replication?

    <p>DNA polymerase I</p> Signup and view all the answers

    How many β clamps are associated with the DNA polymerase III during DNA replication?

    <p>At least two, one on the leading strand and one per Okazaki fragment</p> Signup and view all the answers

    Which strand grows continuously toward the replication fork?

    <p>Leading strand</p> Signup and view all the answers

    What do Okazaki fragments require to begin their synthesis?

    <p>RNA primers</p> Signup and view all the answers

    What happens to the lagging strand during DNA replication?

    <p>It requires a looped structure for polymerases to function together.</p> Signup and view all the answers

    What is the role of helicase in eukaryotic DNA replication?

    <p>Unwind DNA</p> Signup and view all the answers

    Which factor distinguishes DNA Gyrase in bacteria from other type II topoisomerases?

    <p>It specifically removes supercoils.</p> Signup and view all the answers

    Which complex recognizes the origin of replication in eukaryotic cells?

    <p>Origin recognition complex (ORC)</p> Signup and view all the answers

    What does the term 'replisome' refer to?

    <p>The entire complex of active proteins at the replication fork</p> Signup and view all the answers

    What do type I topoisomerases do during DNA replication?

    <p>Relax DNA supercoiling</p> Signup and view all the answers

    What keeps the unwound DNA strands from re-annealing in prokaryotes?

    <p>SSB proteins</p> Signup and view all the answers

    In eukaryotes, when do protein kinases phosphorylate and activate the pre-replication complex?

    <p>During S phase</p> Signup and view all the answers

    What is the primary role of DNA polymerase III during DNA replication?

    <p>To extend RNA primers on the lagging strand.</p> Signup and view all the answers

    What is the function of helicase in DNA replication?

    <p>To unwind the DNA helix.</p> Signup and view all the answers

    Which process is indicated by the Trombone Model in DNA replication?

    <p>Simultaneous elongation of both strands.</p> Signup and view all the answers

    When does DNA polymerase III release the lagging strand?

    <p>When it encounters a previously synthesized Okazaki fragment.</p> Signup and view all the answers

    What activity does DNA polymerase I perform during DNA replication?

    <p>Remove RNA primers and fill gaps with dNTs.</p> Signup and view all the answers

    What is the lagging strand characterized by during replication?

    <p>Synthesis in the opposite direction of unwinding.</p> Signup and view all the answers

    How does the lagging strand allow for two DNA polymerases to work simultaneously?

    <p>By looping the lagging strand.</p> Signup and view all the answers

    What is the backup role of DNA polymerase II during DNA replication?

    <p>To function alongside DNA polymerase III.</p> Signup and view all the answers

    What does primase do during DNA replication?

    <p>Synthesizes RNA primers.</p> Signup and view all the answers

    What is produced when DNA polymerase III extends the RNA primers?

    <p>Okazaki fragments.</p> Signup and view all the answers

    What characterizes the process of nucleosome reassembly on the daughter strand during DNA replication?

    <p>H3H4 tetramers remain intact, while H2A/H2B dimers bind randomly.</p> Signup and view all the answers

    Which statement accurately describes the proofreading function of DNA polymerases in prokaryotes?

    <p>They utilize an exonuclease activity against errors made in nucleotide incorporation.</p> Signup and view all the answers

    During the S phase of the cell cycle, what percentage of replicons is typically actively engaged in replication?

    <p>10-15%</p> Signup and view all the answers

    What is the primary requirement for a dNT to incorporate correctly during DNA replication?

    <p>It must have a complementary base pairing geometry with the template.</p> Signup and view all the answers

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

    <p>It covalently joins 3' dNTs to 5' ends of Okazaki fragments.</p> Signup and view all the answers

    Which statement accurately describes the semi-conservative nature of DNA replication?

    <p>Each daughter duplex contains one parental strand.</p> Signup and view all the answers

    What is the primary role of DNA polymerase in the replication process?

    <p>To synthesize new DNA strands.</p> Signup and view all the answers

    Which feature distinguishes eukaryotic DNA replication from prokaryotic replication?

    <p>Eukaryotic replication is bi-directional from multiple origins.</p> Signup and view all the answers

    What is the function of replication foci in eukaryotic DNA replication?

    <p>To localize the active sites of replication.</p> Signup and view all the answers

    During which phase of the cell cycle is DNA replicated in eukaryotic cells?

    <p>S Phase</p> Signup and view all the answers

    How do DNA replication forks function during the replication process?

    <p>They are the site where new complementary strands are synthesized.</p> Signup and view all the answers

    What is the typical range of active replication origins in human cells during DNA replication?

    <p>10,000 - 100,000 origins</p> Signup and view all the answers

    What is the primary function of Type II topoisomerases in DNA replication?

    <p>To change DNA topology by breaking and rejoining double-stranded DNA</p> Signup and view all the answers

    Which component is specifically utilized for loading the sliding clamp onto DNA during replication in prokaryotes?

    <p>γ-Clamp loading complex</p> Signup and view all the answers

    Why is the lagging strand looped during DNA replication?

    <p>To facilitate simultaneous travel of two DNA polymerases</p> Signup and view all the answers

    What role does DNA Gyrase serve in bacteria?

    <p>To introduce or remove supercoils in DNA</p> Signup and view all the answers

    What is the role of primase during DNA replication in prokaryotes?

    <p>To synthesize RNA primers for lagging strand</p> Signup and view all the answers

    Which statement correctly describes the function of the helicase enzyme during DNA replication?

    <p>It unwinds the double-stranded DNA</p> Signup and view all the answers

    What identifies DNA polymerase III as the primary enzyme in prokaryotic DNA replication?

    <p>It extends RNA primers into DNA</p> Signup and view all the answers

    What distinguishes DNA Polymerase II from DNA Polymerase III in prokaryotes?

    <p>DNA Polymerase II serves primarily as a backup for DNA Polymerase III</p> Signup and view all the answers

    What does the term 'replisome' refer to in prokaryotic DNA replication?

    <p>The complex of proteins active at the replication fork</p> Signup and view all the answers

    During DNA elongation in prokaryotes, where is helicase primarily located?

    <p>On the lagging strand</p> Signup and view all the answers

    What happens to DNA polymerase III when it encounters a previously synthesized Okazaki fragment?

    <p>It releases the lagging strand.</p> Signup and view all the answers

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

    <p>Filling gaps with deoxynucleotides after RNA primer removal.</p> Signup and view all the answers

    Which model explains how the lagging strand allows two DNA polymerases to work simultaneously?

    <p>Trombone Model.</p> Signup and view all the answers

    What role does primase play in DNA replication for prokaryotes?

    <p>Synthesizing RNA primers.</p> Signup and view all the answers

    How does DNA polymerase III incorporate nucleotides during replication?

    <p>By attaching to the RNA primer and incorporating deoxynucleotides.</p> Signup and view all the answers

    What is the significance of the lagging strand being looped during replication?

    <p>It enables two DNA polymerases to replicate simultaneously.</p> Signup and view all the answers

    What process follows the release of the lagging strand by DNA polymerase III?

    <p>The binding of DNA polymerase III further along the lagging strand template.</p> Signup and view all the answers

    What distinguishes DNA polymerase II in relation to DNA polymerase III?

    <p>It serves as a backup polymerase for DNA polymerase III.</p> Signup and view all the answers

    During which phase of replication does primase operate in prokaryotes?

    <p>After the DNA helix is unwound by helicase.</p> Signup and view all the answers

    Which of the following best describes the action of DNA polymerase III on the lagging strand?

    <p>It extends RNA primers by attaching deoxynucleotides.</p> Signup and view all the answers

    What role does DnaB helicase play during prokaryotic DNA replication?

    <p>It unwinds the DNA strands.</p> Signup and view all the answers

    Why are Okazaki fragments necessary during DNA replication?

    <p>They help synthesize RNA primers needed for lagging strand.</p> Signup and view all the answers

    How do protein kinases regulate the pre-replication complex in eukaryotic cells?

    <p>By inhibiting the formation of new pre-RCs.</p> Signup and view all the answers

    In eukaryotic cells, what is the function of type I topoisomerases during DNA replication?

    <p>To relax supercoiled DNA.</p> Signup and view all the answers

    What function does the origin recognition complex (ORC) serve in eukaryotic DNA replication?

    <p>It recognizes the origin of replication.</p> Signup and view all the answers

    What characteristic defines the leading strand during DNA replication?

    <p>It grows continuously towards the replication fork.</p> Signup and view all the answers

    What triggers the phosphorylation and activation of the pre-replication complex during the cell cycle?

    <p>Protein kinases during S phase.</p> Signup and view all the answers

    What is the directionality of new DNA synthesis during replication?

    <p>5' to 3' for both leading and lagging strands.</p> Signup and view all the answers

    What term describes the specific phase of the cell cycle during which DNA is synthesized in eukaryotic cells?

    <p>S Phase</p> Signup and view all the answers

    Which of the following statements about replicons is accurate?

    <p>Each replicon contains one origin of replication.</p> Signup and view all the answers

    What is the role of the replication fork during DNA replication?

    <p>It is the location of strand separation and nucleotide incorporation.</p> Signup and view all the answers

    Which statement best describes the directionality of replication in eukaryotic cells?

    <p>Replication is bi-directional from multiple origins.</p> Signup and view all the answers

    Which factors are involved in the assembly of the DNA polymerase holoenzyme?

    <p>DNA polymerase III and clamp proteins</p> Signup and view all the answers

    During DNA replication, what is the purpose of having multiple replication foci in eukaryotic cells?

    <p>To facilitate the rapid synthesis of large genomes.</p> Signup and view all the answers

    In prokaryotes, how is the function of DNA Gyrase distinct from other type II topoisomerases?

    <p>It is involved in removing supercoils ahead of the replication fork.</p> Signup and view all the answers

    Which of the following best describes the term 'semi-conservative replication'?

    <p>Each daughter DNA molecule retains one original strand.</p> Signup and view all the answers

    What characterizes the lagging strand during DNA replication?

    <p>It contains Okazaki fragments.</p> Signup and view all the answers

    Which protein complex is responsible for recognizing the origin of replication in eukaryotic cells?

    <p>Origin recognition complex (ORC)</p> Signup and view all the answers

    During the initiation of DNA replication, which factor contributes to unwinding the DNA strands in prokaryotes?

    <p>DnaB helicase</p> Signup and view all the answers

    What is the primary function of topoisomerases during DNA replication?

    <p>To relieve supercoiling tension.</p> Signup and view all the answers

    Which statement about the RNA primers in DNA replication is false?

    <p>They are replaced by DNA polymerase II.</p> Signup and view all the answers

    What role do licensing factors play in eukaryotic DNA replication?

    <p>They recruit helicase to the replication origins.</p> Signup and view all the answers

    Which feature distinguishes the synthesis direction of the leading strand during DNA replication?

    <p>It synthesizes in a 5' to 3' direction without interruption.</p> Signup and view all the answers

    What occurs when protein kinases phosphorylate and activate the pre-replication complex in eukaryotes?

    <p>They synchronize DNA replication timing.</p> Signup and view all the answers

    Which is a primary effect of DNA supercoiling during DNA replication?

    <p>It induces tension that requires removal by topoisomerases.</p> Signup and view all the answers

    What is the main function of DNA Gyrase in bacteria?

    <p>It introduces or removes supercoils to alter DNA topology.</p> Signup and view all the answers

    Which statement correctly describes the composition of DNA Polymerase III holoenzyme?

    <p>It contains multiple core polymerases and sliding clamps.</p> Signup and view all the answers

    What role does primase play during DNA replication in prokaryotes?

    <p>It synthesizes RNA primers on both leading and lagging strands.</p> Signup and view all the answers

    Which enzyme is responsible for extending RNA primers on the lagging strand during DNA replication?

    <p>DNA Polymerase III</p> Signup and view all the answers

    How does the structure of the replisome contribute to DNA replication?

    <p>It consists of a complex of various proteins that coordinate replication.</p> Signup and view all the answers

    What is a key feature of the lagging strand during DNA replication?

    <p>It requires multiple RNA primers for synthesis.</p> Signup and view all the answers

    Which characteristic distinguishes type II topoisomerases from type I?

    <p>They change DNA topology by breaking and rejoining double-stranded DNA.</p> Signup and view all the answers

    What critical function do β clamps serve during DNA replication?

    <p>They prevent DNA polymerase from dissociating from the DNA.</p> Signup and view all the answers

    What action does DNA helicase perform during DNA replication?

    <p>It unwinds the double-stranded DNA helix.</p> Signup and view all the answers

    What distinctive feature allows the lagging strand to form a loop during replication?

    <p>It allows two DNA polymerases to work together effectively.</p> Signup and view all the answers

    What is the primary function of DNA polymerase III during the elongation phase of DNA replication?

    <p>Extends RNA primers on the lagging strand</p> Signup and view all the answers

    Which statement accurately describes the function of primase during prokaryotic DNA replication?

    <p>Synthesizes RNA primers on the lagging strand</p> Signup and view all the answers

    What describes the mechanism by which DNA polymerase III continues synthesis on the lagging strand?

    <p>By looping the lagging strand to work ahead</p> Signup and view all the answers

    What occurs immediately after DNA polymerase III encounters a previously synthesized Okazaki fragment?

    <p>It releases the lagging strand template</p> Signup and view all the answers

    What happens to the histone molecules during the nucleosome reassembly on the daughter strand in eukaryotic DNA replication?

    <p>H3H4 tetramers remain intact while H2A/H2B dimers bind randomly.</p> Signup and view all the answers

    Which enzyme is responsible for the removal of RNA primers from Okazaki fragments?

    <p>DNA polymerase I</p> Signup and view all the answers

    Which of the following statements about DNA proofreading in prokaryotes is correct?

    <p>DNA Polymerases I and III utilize a 3'-&gt;5' exonuclease functionality.</p> Signup and view all the answers

    How does DNA polymerase I contribute to DNA replication after removing RNA primers?

    <p>Adds deoxynucleotides to fill in the gap</p> Signup and view all the answers

    Which factor contributes to the high fidelity of DNA replication despite the spontaneous mutation rate?

    <p>The ability to form proper geometric fits of dNTs with the template.</p> Signup and view all the answers

    How many different origins of replication are present in human cells, and what percentage of replicons is typically active during the S phase?

    <p>10,000 to 100,000 origins; ~10-15% of replicons are active.</p> Signup and view all the answers

    What is the primary role of DNA ligase during the DNA replication process?

    <p>Join segments of newly synthesized DNA together.</p> Signup and view all the answers

    Which of the following best describes the overall process of nucleotide incorporation during DNA replication?

    <p>DNA polymerase III extends RNA primers to incorporate nucleotides on the lagging strand</p> Signup and view all the answers

    Which characteristic distinguishes the activity of helicase in prokaryotic DNA replication?

    <p>It unwinds the DNA double helix</p> Signup and view all the answers

    Which statement best reflects the role of DNA polymerase II in the context of DNA replication?

    <p>It functions as a backup for DNA polymerase III</p> Signup and view all the answers

    Study Notes

    DNA Replication

    • Reproduction necessitates copying genetic material
    • DNA replicates during mitosis and meiosis
    • Replication machinery also facilitates DNA repair
    • Human diploid cells have 46 chromosomes (gametes/haploid have 23)

    DNA Replication: Semi-Conservative Replication

    • Watson and Crick model
    • Gradual separation of DNA strands via broken hydrogen bonds
    • Synthesis of two daughter strands complementary to parental templates
    • Each daughter helix contains one strand from the parent structure

    DNA Replication: Bacterial

    • Heavily studied due to temperature-sensitive mutants
    • In vitro culture systems allow controlled gene expression studies
    • More than 30 proteins involved in bacterial DNA replication
    • Similar DNA replication mechanisms in prokaryotes and eukaryotes

    DNA Replication: Eukaryotes

    • Replication occurs during the "Synthesis" phase (S phase) of the cell cycle
    • Eukaryotic DNA is replicated in multiple segments called replicons
    • Human cells possess 10,000-100,000 distinct origins for replication
    • Replication initiates at specific sites, replicon's initiation site in each replicon
    • 10-15% replicons are actively engaged during the S phase
    • Replication proceeds bi-directionally from replication forks
    • Replication forks are sites where the double helix separates, nucleotides are incorporated into a newly synthesized strand

    DNA Replication: Prokaryotes: Initiation

    • DnaA proteins recognize origin recognition complex (OriC)
    • DnaB helicase unwinds the DNA at OriC
    • Single-stranded binding proteins (SSBs) stabilize the unwound strand
    • Primase synthesizes RNA primers

    DNA Replication: Eukaryotes: Initiation

    • Origin recognition complex (ORC) recognizes the origin of replication
    • Licensing factors and helicase are recruited to the origin
    • Numerous proteins, such as Cdc6, Cdt1 facilitate this
    • Helicase is a protein that unwinds DNA molecule

    DNA Replication: Eukaryotes and Prokaryotes: Elongation

    • DNA polymerase III (prokaryotes) and DNA polymerase δ/ε (eukaryotes) are responsible for synthesizing DNA by extending primers
    • DNA polymerase III (prokaryotes) synthesizes both leading and lagging strand DNA simultaneously
    • Two replication forks proceed in opposite directions from a single origin
    • Leading strand synthesizes continuously in the 5' to 3' direction
    • Lagging strand synthesizes discontinuously in the 5' to 3' direction
    • DNA fragments on the lagging strand are called Okazaki fragments
    • Eukaryotic replication requires multiple DNA polymerases, RFC, PCNA
    • DNA polymerase I removes RNA primers, and DNA ligases seals Okazaki fragments

    DNA Replication: Eukaryotes: Elongation

    • DNA polymerase δ/ε synthesizes both the leading and lagging strand
    • DNA replication also proceeds bi-directionally
    • Both leading and lagging strands are synthesized simultaneously
    • Okazaki fragments are synthesized on the laggings strand

    DNA Supercoiling

    • DNA supercoiling occurs during unwinding of DNA
    • Tension built into the structure needs to be relieved by topoisomerases.

    DNA Replication: Eukaryotic Replication Fork:

    • Eukaryotic replication fork utilizes DNA polymerase α, δ, and ε

    DNA Repair

    • DNA is susceptible to damage from environmental factors
    • Spontaneous alteration of DNA
    • Damaged DNA is repaired via various pathways
    • Errors in DNA replication increase the frequency of spontaneous mutations
    • Errors in DNA can lead to genetic diseases
    • Errors in DNA can be caused by ionizing radiation, UV radiation, thermal energy from normal metabolism, and other environmental factors

    DNA Repair: Nucleotide Excision Repair

    • Pathways for repairing bulky lesions (like pyrimidine dimmers, nucleotides)
    • Global genomic and transcription-coupled pathways
    • Crucial for maintaining genomic integrity and preventing diseases

    DNA Repair: Base Excision Repair

    • BER is a pathway for removing altered bases, like uracil, 8-oxoguanine, and 3-methyladenine
    • DNA glycosylase identifies and excises altered bases
    • AP endonuclease cleaves DNA backbone
    • DNA polymerase fills the gap
    • DNA ligase reseals the DNA

    DNA Repair: Double-Strand Breakage Repair

    • NHEJ (non-homologous end joining) is a quick and error-prone repair pathway
    • HR (homologous recombination) is a complex and precise repair pathway that uses a homologous DNA molecule as a template

    DNA Replication and Human Disease

    • Numerous proteins are involved in DNA replication, and mutations in these proteins can lead to genetic diseases.
    • Examples of diseases are premature aging, impaired nervous system development, autoimmune disorders, and various cancers.

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    HSS2305A Spring 2022 DNA Replication Lecture Notes PDF

    Description

    Test your knowledge on DNA replication processes, including its mechanisms in both prokaryotes and eukaryotes. Explore topics such as semi-conservative replication, the Watson and Crick model, and the roles of different proteins involved. This quiz covers essential concepts related to cellular reproduction and genetic information transfer.

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