DNA Replication in Eukaryotes and Prokaryotes
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Questions and Answers

What is a distinguishing feature of DNA replication in eukaryotic cells compared to prokaryotic cells?

  • Prokaryotic cells replicate linear chromosomes.
  • Prokaryotic cells replicate DNA in multiple sites simultaneously.
  • Eukaryotic cells begin replication at multiple origins. (correct)
  • Eukaryotic cells have a single origin of replication.

    • How do prokaryotic chromosome structures differ from eukaryotic chromosome structures?

  • Eukaryotic chromosomes lack a nucleus-like region.
  • Prokaryotic chromosomes are linear and contain histones.
  • Prokaryotic chromosomes are circular and typically supercoiled. (correct)
  • Prokaryotic chromosomes are double-stranded while eukaryotic chromosomes are single-stranded.

    • What role do nucleoid-associated proteins (NAPs) play in prokaryotic cells?

  • They facilitate the supercoiling of prokaryotic DNA. (correct)
  • They assist in the creation of histone clusters around DNA.
  • They form a nuclear membrane surrounding the chromosome.
  • They serve as the primary structure for linear chromosomes.

    • What is true about the chromosome organization in prokaryotic cells?

    <p>Prokaryotic cells generally contain only one circular chromosome.</p> Signup and view all the answers

    What characteristic of prokaryotic chromosomes is NOT accurate?

    <p>They are wrapped around histones for organization.</p> Signup and view all the answers

    What term is used to refer to the DNA found in prokaryotic cells?

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

    Which of the following accurately describes plasmids?

    <p>Independent small DNA molecules with nonessential genes</p> Signup and view all the answers

    In prokaryotic cells, where does DNA replication begin?

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

    What is the function of helicase during the initiation of DNA replication in prokaryotes?

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

    Which of the following characteristics differentiates prokaryotic DNA from eukaryotic DNA?

    <p>Prokaryotic DNA is circular rather than linear</p> Signup and view all the answers

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

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

    How many chromosomes do prokaryotic cells typically contain?

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

    What type of DNA structure is characteristic of prokaryotic replication?

    <p>Circular, double-stranded DNA</p> Signup and view all the answers

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

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

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

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

    What is a key difference between prokaryotic and eukaryotic replication in terms of origins of replication?

    <p>Prokaryotes have a single origin of replication</p> Signup and view all the answers

    Where does DNA replication occur in eukaryotic cells?

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

    What distinguishes the replication process in eukaryotes from that of prokaryotes?

    <p>Eukaryotic replication is more complex and has multiple origins</p> Signup and view all the answers

    Which of these is a requirement specific to eukaryotic replication?

    <p>Presence of histones</p> Signup and view all the answers

    Which of the following statements about the enzymatic activities in replication is correct?

    <p>Eukaryotic replication requires new enzymatic activities for the ends of chromosomes</p> Signup and view all the answers

    How do the replication machinery of prokaryotes and eukaryotes compare?

    <p>Eukaryotic machinery resembles that of bacteria but is more complex</p> Signup and view all the answers

    What role does single-stranded binding protein play in DNA replication?

    <p>It prevents reannealing of separated DNA strands.</p> Signup and view all the answers

    How does the leading strand differ from the lagging strand during DNA synthesis?

    <p>The leading strand synthesis proceeds continuously.</p> Signup and view all the answers

    What is the function of DNA ligase in DNA replication?

    <p>To seal the gaps between Okazaki fragments.</p> Signup and view all the answers

    Which of the following describes the synthesis direction of both leading and lagging strands?

    <p>Both are synthesized in the 5’-3’ direction.</p> Signup and view all the answers

    What happens to RNA primers once the synthesis of Okazaki fragments is complete?

    <p>They are removed by exonuclease activity of DNA polymerase I.</p> Signup and view all the answers

    What constitutes a functional unit in the replication complex during DNA synthesis?

    <p>Helicase and primase form a primosome.</p> Signup and view all the answers

    During the termination of DNA replication, what is recognized at the replication fork?

    <p>Termination sequences (ter).</p> Signup and view all the answers

    Which enzyme is primarily responsible for adding nucleotides during the synthesis of the lagging strand?

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

    What initiates the synthesis of new Okazaki fragments after the completion of the first set?

    <p>Dissociation of core subunits from sliding clamps.</p> Signup and view all the answers

    Study Notes

    DNA Replication in Eukaryotes

    • Eukaryotes typically have linear chromosomes
    • DNA replication begins at multiple origins of replication along each chromosome
    • Eukaryotic cells generally have more DNA than prokaryotic cells
    • Prokaryotic cells have a single circular chromosome, while eukaryotic cells typically contain multiple linear chromosomes
    • DNA replication in prokaryotic cells starts at a single origin of replication
    • DNA replication in eukaryotic cells starts at multiple origins

    Prokaryotic Chromosome Structure

    • Prokaryotic chromosomes are found in the nucleoid of prokaryotic cells
    • Prokaryotic chromosomes are circular in shape
    • Prokaryotic cells do not have a membrane-bound nucleus
    • The genetic material of prokaryotes is located in a region of the cytoplasm called the nucleoid
    • A prokaryotic cell typically has only a single, coiled, circular chromosome
    • Some prokaryotes have more than one circular chromosome (e.g., Vibrio cholerae)
    • The nucleoid is an irregularly shaped region within the prokaryotic cell containing most of the genetic material, but not surrounded by a nuclear membrane

    Prokaryotic Chromosome Structure

    • Prokaryotic cells have only one chromosome
    • This chromosome must be condensed and supercoiled to fit inside a small space
    • Most prokaryotic cells do not use histones for DNA packing
    • Prokaryotic DNA undergoes supercoiling, facilitated by nucleoid-associated proteins (NAPs) instead of histones
    • NAPs are proteins in the nucleoid that bind to the DNA molecule
    • The DNA of prokaryotic cells is referred to as the genophore

    Binary Fission

    • Many prokaryotes, such as bacteria, reproduce via binary fission, a method of asexual reproduction
    • Prokaryotic cells also carry small molecules of DNA called plasmids
    • Plasmids are small, circular DNA molecules that contain nonessential genes
    • Plasmids can vary in size and usually have a small number of genes
    • Plasmids replicate independently of the cell's main chromosome

    Summary of Prokaryotic Replication

    • DNA replication is a fundamental process in all living organisms, consisting of three major steps: initiation, elongation, and termination
    • In E. coli, the replication origin is called Oric, composed of 245 base pairs
    • The binding of helicase is key to replication initiation.
    • Helicase activity unwinds the DNA strand.
    • Topoisomerase relieves supercoiling during DNA replication.
    • DNA polymerase adds nucleotides to the template strand to synthesize a new strand
    • The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments (Okazaki fragments)

    Eukaryotic Replication

    • Eukaryotic replication is a more complex process that occurs only during the S phase of the cell cycle
    • Pre-initiation events occur in G1 phase
    • Eukaryotic replication is bidirectional and starts at numerous origins of replication
    • Replication machinery in eukaryotes resembles that of bacteria, but is larger and more complex
    • Eukaryotic DNA replication requires more factors to assemble helicase and primase complexes

    Eukaryotic Replication Enzymology

    • Helicase unwinds the DNA helix
    • SSB proteins stabilize separated strands.
    • Topoisomerase prevents supercoiling
    • DNA polymerase synthesize new DNA strand
    • Primase synthesizes RNA primers
    • DNA polymerase extends RNA primers
    • Okazaki fragments are formed
    • DNA ligase seals nicks in the newly synthesized strand
    • DNA topoisomerases relieve tension in DNA replication

    Eukaryotic Replication Features

    • Eukaryotic replication is bidirectional, with origins of replication at multiple locations on each chromosome.
    • DNA replication results in a double-stranded DNA molecule with one parental strand and one newly synthesized daughter strand.
    • Synthesis of DNA occurs in the 5' to 3' direction
    • Synthesis occurs only in the S phase
    • The result is a doubling of DNA for cell division.
    • Okazaki fragments are characteristic of lagging strand synthesis

    Summary of DNA Replication

    • Prokaryotic DNA is found freely in the cytoplasm, in a circular form.
    • Eukaryotic DNA is found within the nucleus, in a linear form.
    • Introns are present in eukaryotic coding regions, but absent in prokaryotic DNA.
    • Prokaryotes have a single chromosome, while eukaryotes have multiple chromosomes.

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    DNA Replication in Eukaryotes Lecture 4 PDF

    Description

    Explore the differences in DNA replication and chromosome structure between eukaryotic and prokaryotic cells. This quiz covers topics such as the nature of chromosomes, origins of replication, and the structure of genetic material in both cell types.

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