DNA Replication Overview
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Questions and Answers

What is the primary purpose of DNA replication?

  • To repair damaged DNA
  • To create variations in genetic material
  • To duplicate DNA for cell division
  • To convert DNA into RNA (correct)
  • Prokaryotic DNA replication happens in the nucleus of the cell.

    True

    What are the three main steps of eukaryotic DNA replication?

    Initiation, elongation, and termination.

    During DNA replication, the two strands of the DNA molecule separate and new __________ strands are produced.

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

    Match the following types of DNA replication with their characteristics:

    <p>Eukaryotic DNA Replication = Occurs in the nucleus Prokaryotic DNA Replication = Occurs in the cytoplasm Replication Fork = Site of DNA strand separation DNA Polymerase III = Enzyme for adding nucleotides in prokaryotes</p> Signup and view all the answers

    Which enzyme is responsible for unwinding the DNA during replication?

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

    DNA replication is a conservative process, resulting in two original DNA strands.

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

    In which direction are nucleotides added during prokaryotic DNA replication?

    <p>5’ to 3’ direction.</p> Signup and view all the answers

    What role does DNA helicase play during DNA replication?

    <p>It breaks hydrogen bonds between base pairs.</p> Signup and view all the answers

    Single-strand binding (SSB) proteins are not necessary during DNA replication.

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

    What are Okazaki fragments?

    <p>Short segments of DNA synthesized on the lagging strand during replication.</p> Signup and view all the answers

    During DNA replication, __________ proofreads the new strands and corrects any errors.

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

    Match the following terms with their definitions:

    <p>Helicase = Unzips DNA strands Topoisomerase = Relieves tension in supercoils Primase = Synthesizes RNA primers DNA Ligase = Joins Okazaki fragments</p> Signup and view all the answers

    Which of the following statements is true regarding DNA replication in eukaryotes?

    <p>Replication forks form at multiple origins.</p> Signup and view all the answers

    The leading strand is synthesized discontinuously, while the lagging strand is synthesized continuously.

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

    What is the function of DNA ligase?

    <p>To bond the sugar-phosphate backbone and seal gaps between Okazaki fragments.</p> Signup and view all the answers

    What is the average length of a eukaryotic chromosome?

    <p>1 x 10^8 base pairs</p> Signup and view all the answers

    Telomerase is necessary for filling the gaps left at the ends of linear chromosomes.

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

    What is the replication rate of a eukaryotic chromosome?

    <p>100 base pairs per second</p> Signup and view all the answers

    In prokaryotic replication, the DNA replicates in the ______.

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

    Match the terms to their definitions:

    <p>Telomeres = Repeated sequences at the ends of chromosomes Nucleosomes = Units of DNA wrapped around histones Replication Forks = Y-shaped structures where DNA is being replicated DNA Polymerase = Enzyme that synthesizes new DNA strands</p> Signup and view all the answers

    How many origins of replication are present in eukaryotic cells?

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

    Eukaryotic chromosomes can be shorter after each round of replication due to incomplete replication at the ends.

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

    What are the major differences between prokaryotic and eukaryotic replication regarding the speed and number of DNA polymerases involved?

    <p>Prokaryotic replication is faster (2000 base pairs/sec) and involves DNA polymerases I and III, while eukaryotic replication is slower (100 base pairs/sec) and involves DNA polymerases α, δ, and ε.</p> Signup and view all the answers

    Study Notes

    DNA Replication

    • DNA replication is the process of creating two identical copies of a DNA molecule
    • DNA replication occurs before cell division to ensure each daughter cell receives a complete set of DNA
    • Both prokaryotes and eukaryotes replicate DNA semi-conservatively, meaning each new DNA molecule contains one original strand and one newly synthesized strand

    Prokaryotic and Eukaryotic Differences

    • Prokaryotic DNA is circular and located in the cytoplasm
    • Eukaryotic DNA is linear and located in the nucleus
    • Prokaryotes have a single origin of replication, while eukaryotes initiate replication at multiple origins

    DNA Replication Steps

    • DNA replication occurs in three steps: initiation, elongation, and termination
    • The process starts with the unwinding of the DNA double helix, which is carried out by the enzyme helicase
    • Single-strand binding proteins (SSBs) stabilize the separated strands, preventing them from re-annealing
    • DNA polymerase adds nucleotides to the newly synthesized strand, following the base pairing rules (A with T, and G with C)
    • DNA polymerase I proofreads the newly synthesized strands, correcting any errors
    • DNA ligase joins the newly synthesized fragments together

    Leading and Lagging Strands

    • Replication occurs in both directions from the origin, creating two replication forks
    • One strand, the leading strand, is synthesized continuously in the 5’ to 3’ direction
    • The other strand, the lagging strand, is synthesized discontinuously in short fragments called Okazaki fragments

    Telomeres

    • Telomeres are repetitive sequences at the ends of linear eukaryotic chromosomes
    • Telomerase, an enzyme with an RNA component, adds these repeated sequences, preventing chromosome shortening during replication

    Prokaryotic vs. Eukaryotic Replication

    • Prokaryotic replication occurs in the cytoplasm, while eukaryotic replication occurs in the nucleus
    • Prokaryotic replication is faster than eukaryotic replication
    • Prokaryotic DNA is circular, while eukaryotic DNA is linear
    • Prokaryotes use DNA polymerase I and III, while eukaryotes use DNA polymerase α, δ, and ε

    Replication of Circular DNA

    • In some prokaryotes, replication begins at a single origin and continues in two directions until the entire chromosome is copied
    • The resulting structure looks like the Greek letter theta (θ)

    Rolling Circle Model

    • This model is common in bacteriophages and uses a nick at the origin of replication to initiate DNA synthesis
    • The 5' end of the molecule is displaced and acts as a primer, allowing for continuous replication and multiple copies of the genome

    Eukaryotic Chromosome Replication

    • Eukaryotes replicate their chromosomes during the S phase of the cell cycle
    • The process requires multiple origins of replication to ensure efficient replication of the large eukaryotic genome

    Checkpoints in Eukaryotic Replication

    • Several checkpoints ensure proper DNA replication before cell division
    • These checkpoints include proteins called cyclins and enzymes called cyclin-dependent kinases (Cdks)
    • These ensure the cell is large enough, the environment is favorable, all DNA is replicated, and chromosomes are attached to the mitotic spindle

    Nucleosome Assembly

    • During replication, nucleosomes must disassemble and reassemble
    • New histones and associated chromatin proteins must be synthesized for the newly formed DNA molecules

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    Description

    This quiz covers the essential processes of DNA replication, including the differences between prokaryotic and eukaryotic DNA. Learn about the three main steps of replication: initiation, elongation, and termination. Test your understanding of how DNA ensures accurate genetic transmission during cell division.

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