DNA Replication Quiz
48 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which statement correctly describes the fidelity of DNA replication?

  • It must possess a very high degree of fidelity. (correct)
  • It depends on the nutrient availability in the cell.
  • It is moderate and allows for frequent errors.
  • It is not crucial for cell survival.

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

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

    • Which of the following characteristics is NOT true about the process of DNA replication?

  • It can occur multiple times during one cell cycle. (correct)
  • It involves the whole genome.
  • It requires a primer for initiation.
  • It is semiconservative.

    • Which of the following processes is NOT involved in the mechanics of DNA replication?

    <p>Elongation of protein chains (C)</p> Signup and view all the answers

    What is the direction of DNA synthesis during replication?

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

    What is the role of DNA polymerase in E. coli during replication?

    <p>To catalyze the replication of DNA (A)</p> Signup and view all the answers

    Which statement is true about the nature of DNA replication?

    <p>It occurs simultaneously in both strands. (D)</p> Signup and view all the answers

    Which of the following enzymes are NOT DNA polymerases identified in E. coli?

    <p>DNA polymerase-IV (B)</p> Signup and view all the answers

    What is the primary function of primase during DNA replication?

    <p>Builds RNA primers that are complementary to DNA templates. (B)</p> Signup and view all the answers

    Which statement accurately describes the leading strand during DNA replication?

    <p>It is synthesized continuously in the 5' to 3' direction. (C)</p> Signup and view all the answers

    Which of the following best characterizes the lagging strand during replication?

    <p>It requires short segments called Okazaki fragments for synthesis. (B)</p> Signup and view all the answers

    What role does DNA polymerase III play in the synthesis of the leading strand?

    <p>It synthesizes DNA utilizing the free 3' OH group from an RNA primer. (B)</p> Signup and view all the answers

    Where is the lagging strand located relative to the leading strand at the replication fork?

    <p>It is located on the opposite side of the replication fork. (C)</p> Signup and view all the answers

    What is the approximate length of the RNA primers synthesized by primase?

    <p>Approximately 10 nucleotides long. (C)</p> Signup and view all the answers

    What prevents DNA polymerase III from synthesizing the lagging strand continuously?

    <p>The antiparallel nature of DNA strands. (B)</p> Signup and view all the answers

    What are Okazaki fragments?

    <p>Short segments of DNA synthesized on the lagging strand. (A)</p> Signup and view all the answers

    What role do single stranded binding proteins (SSB) play during DNA replication?

    <p>They prevent the unwound strands from re-winding together. (A)</p> Signup and view all the answers

    Which enzyme is mainly responsible for the elongation of both leading and lagging strands during DNA replication?

    <p>DNA polymerase (B)</p> Signup and view all the answers

    In which direction do DNA polymerases synthesize new DNA strands?

    <p>5′→3′ direction (D)</p> Signup and view all the answers

    What initial protein binds to the origin of replication to start the DNA unwinding process?

    <p>DnaA protein (C)</p> Signup and view all the answers

    What type of topoisomerase cuts both strands of the DNA double helix?

    <p>Type II topoisomerase (C)</p> Signup and view all the answers

    Why do DNA replication enzymes encounter positive supercoils ahead of the replication fork?

    <p>Due to the unwinding of DNA creating tension. (A)</p> Signup and view all the answers

    Which of the following statements about DNA polymerases is false?

    <p>They can add nucleotides in the 3′→5′ direction. (D)</p> Signup and view all the answers

    What is the consequence of having multiple units of DnaA protein at the origin of replication?

    <p>Enhanced helicase activation and DNA unwinding (C)</p> Signup and view all the answers

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

    <p>Join DNA fragments together (A)</p> Signup and view all the answers

    During replication, what distinguishes the leading strand from the lagging strand?

    <p>Leading strand synthesis occurs in a 5' to 3' direction (D)</p> Signup and view all the answers

    What role does DNA polymerase I play during DNA replication?

    <p>It proofreads the DNA and repairs mismatches. (C)</p> Signup and view all the answers

    What type of bond does DNA ligase create between deoxyribonucleotides?

    <p>Phosphodiester bonds (A)</p> Signup and view all the answers

    Which enzyme is responsible for synthesizing the bulk of the E.coli genome?

    <p>DNA polymerase III (D)</p> Signup and view all the answers

    Which activity of DNA polymerase III allows it to correct errors during DNA synthesis?

    <p>Its 3' to 5' exonuclease activity (D)</p> Signup and view all the answers

    Okazaki fragments are formed during the synthesis of which strand?

    <p>Lagging strand (A)</p> Signup and view all the answers

    What is the function of single-strand binding proteins (SSB) during DNA replication?

    <p>They stabilize single-stranded DNA. (D)</p> Signup and view all the answers

    Which of the following eukaryotic DNA polymerases is responsible for mitochondrial DNA replication?

    <p>Pol-γ (A)</p> Signup and view all the answers

    What is the function of RNA primers in DNA replication?

    <p>To initiate synthesis of DNA strands (D)</p> Signup and view all the answers

    How does DNA polymerase I remove RNA primers during replication?

    <p>Through 5′→3′ exonuclease activity. (C)</p> Signup and view all the answers

    What role does DNA polymerase III play in alleviating supercoiling during DNA replication?

    <p>By assisting helicase in unwinding DNA (D)</p> Signup and view all the answers

    What is the consequence of a malfunctioning DNA polymerase III during synthesis?

    <p>Higher likelihood of incorrect nucleotide incorporation (D)</p> Signup and view all the answers

    Which accessory protein is primarily responsible for alleviating torsional stress during DNA replication?

    <p>Topoisomerase (C)</p> Signup and view all the answers

    In what manner does DNA polymerase proofread newly synthesized DNA?

    <p>By utilizing 3′→5′ exonuclease activity. (C)</p> Signup and view all the answers

    What is the primary function of DNA ligase in DNA replication?

    <p>To join Okazaki fragments on the lagging strand. (D)</p> Signup and view all the answers

    What is the primary purpose of DNA repair mechanisms?

    <p>To maintain genomic integrity and prevent the propagation of mutations (A)</p> Signup and view all the answers

    Which of the following is NOT a mechanism of DNA repair?

    <p>Exonuclease trim repair (ETR) (B)</p> Signup and view all the answers

    How does methylation play a role in mismatch repair?

    <p>Methylation helps to identify the correct strand by its degree. (C)</p> Signup and view all the answers

    What type of damage occurs as a result of UV light exposure?

    <p>Covalent joining of adjacent pyrimidines, forming dimers (B)</p> Signup and view all the answers

    What role does DNA ligase play in DNA repair mechanisms?

    <p>It fills in gaps left by removal of damaged nucleotides. (B)</p> Signup and view all the answers

    Which statement accurately describes the process of base excision repair?

    <p>It involves the recognition and excision of damaged single bases. (D)</p> Signup and view all the answers

    What is the first step in most DNA repair mechanisms?

    <p>Recognition of the damage on the DNA (C)</p> Signup and view all the answers

    Which of the following accurately describes hemimethylation in DNA repair?

    <p>Only the parental strand is methylated immediately after synthesis. (A)</p> Signup and view all the answers

    Flashcards

    DNA Replication

    The process of creating an identical copy of DNA.

    Semiconservative Replication

    Each new DNA molecule contains one original strand and one newly synthesized strand.

    Bidirectional Replication

    DNA replication occurs in both directions from a single starting point.

    Origin of Replication

    Specific starting point for DNA replication.

    Signup and view all the flashcards

    Replication Fork

    Y-shaped region where DNA is split during replication.

    Signup and view all the flashcards

    DNA Polymerase

    Enzyme that adds nucleotides to a growing DNA strand.

    Signup and view all the flashcards

    S phase

    Phase of the cell cycle where DNA replication occurs.

    Signup and view all the flashcards

    Cell Cycle

    Series of events that a cell goes through as it grows and divides.

    Signup and view all the flashcards

    DNA Replication Origin

    Specific location on a DNA molecule where DNA replication begins.

    Signup and view all the flashcards

    DNA Helicase

    Enzyme that unwinds the DNA double helix during replication.

    Signup and view all the flashcards

    Single-Strand Binding Proteins (SSBs)

    Proteins that prevent separated DNA strands from reannealing.

    Signup and view all the flashcards

    Topoisomerases

    Enzymes that relieve DNA supercoiling ahead of the replication fork.

    Signup and view all the flashcards

    Leading Strand

    DNA strand synthesized continuously in the 5' to 3' direction.

    Signup and view all the flashcards

    Lagging Strand

    DNA strand synthesized discontinuously in short fragments (Okazaki fragments).

    Signup and view all the flashcards

    DNA Ligase

    Enzyme that joins Okazaki fragments together.

    Signup and view all the flashcards

    Okazaki Fragments

    Short DNA fragments synthesized on the lagging strand during DNA replication.

    Signup and view all the flashcards

    3' to 5' Exonuclease

    A proofreading function of DNA polymerase III that removes incorrectly added nucleotides from the newly synthesized DNA strand.

    Signup and view all the flashcards

    What are the two main enzymes involved in the synthesis of the lagging strand?

    DNA polymerase III and DNA polymerase I are the two main enzymes involved in the synthesis of the lagging strand. DNA polymerase III synthesizes the Okazaki fragments, while DNA polymerase I removes the RNA primers and replaces them with DNA.

    Signup and view all the flashcards

    UV Damage

    Exposure to UV light can cause adjacent pyrimidines, usually thymines, to form a covalent bond, creating a dimer. This blocks DNA polymerase, preventing DNA replication.

    Signup and view all the flashcards

    Mismatch Repair

    A process that corrects mismatched nucleotide pairs in newly synthesized DNA.

    Signup and view all the flashcards

    Methylation in Mismatch Repair

    Mismatch repair relies on methylation to distinguish the original, correct DNA strand from the newly synthesized strand that might have a mismatch.

    Signup and view all the flashcards

    Excision Repair

    A general repair mechanism that removes damaged DNA segments.

    Signup and view all the flashcards

    Nucleotide Excision Repair (NER)

    Excision repair that removes a segment of DNA containing damaged nucleotides, including bulky lesions like thymine dimers.

    Signup and view all the flashcards

    Base Excision Repair (BER)

    Excision repair that removes individual damaged bases from the DNA, often removing damaged bases due to chemical damage.

    Signup and view all the flashcards

    Homologous Recombination (HR)

    Repair mechanism for double-stranded DNA breaks (DSBs) that uses the undamaged sister chromatid as a template to repair the break.

    Signup and view all the flashcards

    Nonhomologous End Joining (NHEJ)

    Repair mechanism for double-stranded DNA breaks (DSBs) that directly re-ligates the broken ends, sometimes with a small loss of nucleotides.

    Signup and view all the flashcards

    Primer

    A short RNA sequence that is complementary to the DNA template and provides a free 3' OH group for DNA polymerase to start synthesizing DNA.

    Signup and view all the flashcards

    Primase

    An enzyme that synthesizes short RNA primers during DNA replication.

    Signup and view all the flashcards

    DNA polymerase III

    This enzyme is the primary replicator of the E.coli genome, responsible for adding new DNA nucleotides to the growing chain, making it the workhorse of DNA replication.

    Signup and view all the flashcards

    Proofreading

    The process by which DNA polymerases check for and correct any errors in newly synthesized DNA strands, ensuring accuracy in replication.

    Signup and view all the flashcards

    Discontinuous synthesis

    The process of synthesizing DNA in short fragments on the lagging strand due to the 5' to 3' directionality of DNA polymerase.

    Signup and view all the flashcards

    RNA primase

    This enzyme lays down short RNA primers on the template strand, providing a starting point for DNA polymerase to begin adding nucleotides.

    Signup and view all the flashcards

    Why is a primer needed?

    DNA polymerase cannot initiate DNA synthesis without a free 3' OH group. The primer provides this starting point.

    Signup and view all the flashcards

    How does DNA polymerase synthesize?

    DNA polymerase can only add nucleotides to a pre-existing 3' OH group, and it synthesizes DNA in the 5' to 3' direction.

    Signup and view all the flashcards

    Study Notes

    DNA Replication Overview

    • DNA replication is the process of creating two identical DNA molecules from a single original DNA molecule.
    • This is crucial for cell division, ensuring each daughter cell receives a complete set of genetic instructions.
    • Cells continually divide (e.g., stem cells) or divide a specific number of times until death.
    • During cell division, everything within the cell must be duplicated for the survival of the resulting daughter cells.
    • DNA replication is the synthesis of a new DNA strand from the existing template DNA, creating an identical copy.
    • DNA replication must be highly accurate
    • The process is complex, involving multiple enzymatic activities.
    • Replication occurs during the S phase of the cell cycle.
    • It starts at specific sites in DNA (origins of replication).
    • It involves several enzymes and proteins.
    • Replication occurs once during a cell cycle and involves the entire genome.
    • Replication is template-dependent, guided by base pairing.
    • Replication requires a primer for initiation.
    • Replication is semiconservative (each new DNA molecule contains one original strand and one new strand.)
    • Replication proceeds in a 5' to 3' direction.
    • Replication occurs bidirectionally and simultaneously in both strands.
    • DNA replication is semi-discontinuous.

    Central Dogma of Molecular Biology

    • The flow of genetic information in a biological system is often described as the central dogma.
    • The central dogma is a statement that describes the flow of information from DNA to RNA to protein.
    • DNA replicates to create more DNA.
    • DNA is transcribed into RNA.
    • RNA is translated into protein.

    DNA Replication Steps

    • Identification of origin of replication
    • Unwinding of double-stranded DNA
    • Formation of replication bubbles
    • Establishment of replication fork(s)
    • Initiation of DNA synthesis
    • Elongation of DNA
    • Termination
    • Reconstitution of chromatin structure

    Replication Proteins

    • Processivity accessory proteins
    • Helicase: unwinds the DNA double helix
    • Single-strand binding proteins: stabilize the separated DNA strands.
    • Primase: synthesizes short RNA primer sequences
    • Topoisomerases: relieve torsional stress during unwinding
    • DNA polymerase (pol) I, II, and III: synthesize complementary DNA strands; pol I also involved in primer removal and gap filling
    • DNA ligase: seals the gaps between DNA fragments.

    DNA Polymerase I

    • It's the most common replicating enzyme in E. coli
    • Removes RNA primers from the lagging strand, essential for DNA synthesis.
    • It is involved in proofreading, repairing damaged or mismatched DNA.
    • The polymerase has 5'→ 3' polymerase as well as 3'→ 5' exonuclease activity.
    • 5'→3' polymerase activity: replacing RNA primer with DNA
    • 3'→5' exonuclease activity: proofreading the synthesized new chain

    DNA Polymerase II

    • It is involved in proofreading and repairing damaged DNA.

    DNA Polymerase III

    • Responsible for bulk replication of the E. coli genome.
    • Much more active than pol I but less abundant than it.
    • Its main role is in replicating DNA.

    Eukaryotic DNA Polymerases

    • Five distinct eukaryotic DNA polymerases (alpha, beta, gamma, delta, epsilon) have been identified.
    • Each is specialized for specific functions in replication – subcellular localization as well as their replicative activities.
    • Pol δ and ε are equivalent to E. coli Pol III
    • Pol α is equivalent to E. coli Pol I
    • Pol γ replicates mitochondrial DNA, and Pol β performs DNA repair.

    DNA Replication Direction

    • Synthesis of new DNA strands occurs in the 5' to 3' direction, antiparallel to the template strand.

    Leading and Lagging Strands

    • Leading strand: synthesized continuously in the same direction as the replication fork's movement.
    • Lagging strand: synthesized discontinuously in fragments (Okazaki fragments) in the opposite direction. Okazaki fragments are joined by DNA ligase creating a continuous strand.

    Okazaki Fragments

    • Short segments of DNA formed on the lagging strand during DNA replication.
    • Short stretches of RNA are incorporated into the strand and extended using DNA polymerase.
    • They are later removed and replaced by DNA, then joined by DNA ligase.

    Replication Termination

    • Leading strand closes in on lagging strand
    • Ligase completes new strand
    • Daughter strands paired with original strands resulting in semi-conservative replication
    • Various proteins work together along the replication fork.

    DNA Repair

    • DNA is constantly subjected to environmental insults which can cause alterations or removal of nucleotide bases.
    • Repair is critical for maintaining genomic integrity and preventing mutations.
    • Repair systems involve:
    • Recognition of the damage on the strand, removal/excision of lesion.
    • Gap filling, using sister strand as template for DNA repair
    • Ligation.
    • Excision repair can be into nucleotide excision and base excision.
    • Methyl-directed mismatch repair, involves methylation for discrimination steps.
    • Repair of damage due to UV light (pyrimidine dimers) involves several steps to repair the damage
    • Non-homologous end joining (NHEJ) alters the original DNA sequence during repair and is used to repair double strand breaks when the cells have not yet duplicated their DNA.
    • Homologous recombination is a more challenging repair pathway to accomplish but restores the original DNA sequence. It typically occurs after DNA duplication

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    DNA Replication Lecture Notes PDF

    Description

    Test your knowledge of DNA replication with this quiz that covers key concepts such as the role of enzymes, the fidelity of replication, and characteristics of leading and lagging strands. Understand the processes involved and the particulars of DNA polymerase functions, particularly in E. coli. Challenge yourself and see how well you grasp this fundamental biological process!

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser