DNA Replication in Biological Systems Part I-B (Exam 1)

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Questions and Answers

Which of the following is NOT a factor that contributes to productivity?

  • Exercise
  • Healthy eating
  • Time Off
  • Hard work (correct)
  • Sleep

Which of the following is NOT a topic covered in Part I-B?

  • DNA content of cells
  • Cell cycle
  • Protein synthesis (correct)
  • DNA replication

What is the C-value of a set of chromosomes?

  • The weight of one set of chromosomes (pg) (correct)
  • The number of chromosomes in one set
  • The total amount of DNA in a cell
  • None of the above

What is the haploid number of chromosomes in humans?

<p>23</p> Signup and view all the answers

Homologous chromosomes carry the same genes at the same loci.

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

DNA replication occurs during both mitosis and meiosis.

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

DNA replication proceeds in only one direction.

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

What is the primary function of DnaB in DNA replication?

<p>It is a helicase that unwinds the DNA double helix (B)</p> Signup and view all the answers

What is the name of the specific site on the E. coli chromosome where DNA replication initiates?

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

What is the role of TUS protein in DNA replication termination?

<p>It binds to terminator sequences, preventing further replication fork movement.</p> Signup and view all the answers

Eukaryotic genomes are typically smaller than bacterial genomes.

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

What is the primary difference between prokaryotic and eukaryotic DNA replication in terms of origin of replication?

<p>Eukaryotes have multiple origins of replication, while prokaryotes have only one. (A)</p> Signup and view all the answers

What are the two main types of DNA replication processes?

<p>Continuous and discontinuous</p> Signup and view all the answers

Telomeres are found at the ends of linear chromosomes and prevent the loss of genetic information during replication.

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

What is the role of the sliding clamp in DNA replication?

<p>To hold the DNA polymerase in place as it moves along the template strand (D)</p> Signup and view all the answers

The cell cycle of eukaryotes includes a resting phase (G0) where cells are not actively dividing.

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

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

<p>To join DNA fragments together (E)</p> Signup and view all the answers

In eukaryotes, sister chromatids are held together by cohesins.

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

What is the name of the protein that cleaves cohesins during anaphase?

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

The human genome is 1200 times larger than the E. coli genome.

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

Eukaryotic replisomes replicate DNA at a much faster rate than prokaryotic replisomes.

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

What is the primary difference between prokaryotic and eukaryotic DNA replication in terms of the structure of their chromosomes?

<p>Eukaryotes have linear chromosomes, while prokaryotes have circular chromosomes. (A)</p> Signup and view all the answers

Okazaki fragments are larger in prokaryotes than in eukaryotes.

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

Eukaryotic DNA replication has a formal termination sequence.

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

Eukaryotic DNA replication occurs only during the S phase of the cell cycle.

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

The ______ phase is where a cell prepares for DNA replication by growing in size and synthesizing essential molecules.

<p>G1</p> Signup and view all the answers

Which of the following processes are NOT involved in eukaryotes' DNA replication?

<p>Protein synthesis (E)</p> Signup and view all the answers

In eukaryotes, DNA replication occurs only at the S phase of the cell cycle.

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

Match the following proteins with their functions in DNA replication:

<p>DnaB = Helicase, unwinds DNA DnaG = Primase, synthesizes RNA primers DNA ligase = Joins DNA fragments together DNA polymerase = Adds nucleotides to the growing DNA strand DnaA = Binds to the origin of replication SSB = Single-stranded binding protein, stabilizes single-stranded DNA Gyrase = Introduces negative supercoils into DNA</p> Signup and view all the answers

Why is the process of DNA replication important?

<p>All of the above (D)</p> Signup and view all the answers

Flashcards

DNA content of cells

The amount of DNA in a cell, measured by the number of chromosomes and the weight of a single set (e.g., C-value).

Cell cycle (eukaryotes)

The series of events that lead to cell division in eukaryotic cells, including DNA replication and mitosis or meiosis.

DNA replication (E. coli)

The process of copying DNA in bacteria (E. coli) prior to binary fission, starting from a single origin and proceeding in both directions along the circular chromosome.

Differences DNA replication (prokaryotes vs eukaryotes)

Prokaryotic replication is simpler (single origin, faster), while eukaryotic replication is more complex (multiple origins, slower), related to genome size and structure.

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Meiosis (eukaryotes)

A specialized type of cell division in eukaryotes that reduces the chromosome number and generates gametes (sex cells).

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n-value

The number of chromosomes in a single set of chromosomes; a gamete's chromosome count.

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C-value

The amount of DNA contained in a single set of chromosomes (measured in picograms).

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Homologous pair

A pair of chromosomes with similar DNA sequences, including specific genes at the same loci.

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Mitosis

A type of cell division that results in two daughter cells from one parent cell, maintaining the chromosome number.

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Sister chromatids

Identical copies of a single replicated chromosome held together.

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Origin of Replication (OriC)

Specific sequence on a DNA molecule where DNA replication starts.

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Elongation (replication)

The process of adding nucleotides to the growing DNA strand.

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RNA primers

Short RNA sequences that initiate DNA synthesis.

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Termination (replication)

The final stage of DNA replication, where replication stops at specific sites.

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Decatenase

Enzyme that disentangles or unwinds intertwined DNA molecules.

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Telomeres

Protective caps at the ends of linear chromosomes, preventing loss of genetic material.

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Okazaki fragments

Short DNA fragments synthesized discontinuously on the lagging strand.

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Replisome

Large enzyme complex responsible for DNA replication.

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Continuous DNA synthesis

DNA replication on the leading strand occurs in one continuous direction, in the same direction as the replication fork.

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Discontinuous DNA synthesis

DNA replication on the lagging strand occurs in short, backward-facing segments called Okazaki fragments.

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Gyrase

Enzyme that relieves torsional stress during DNA replication by unwinding DNA.

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Study Notes

Productivity Myth vs. Reality

  • Perceived productivity: Hard work is the key.
  • Actual reality: Exercise, healthy eating, and sleep are more effective for productivity. Time off is also important.

DNA Replication in Biological Systems

  • Part I-B: This section focuses on the DNA content in cells, the cell cycle in eukaryotes, DNA replication in E. coli, comparing DNA replication between prokaryotes and eukaryotes, and meiosis in eukaryotes.
  • DNA content of cells: n-value is the number of chromosomes in a single set. C-value is the weight of a single set of chromosomes in picograms (pg). Gametes are reference points for animals for their n chromosomes and C DNA content.
  • Human Chromosomes: Humans have 46 chromosomes (2n = 46); males have 6.41 pg of DNA, and females have 6.51 pg. Homologous pairs have similar DNA sequences, the same genes located at the same loci, and the same centromere location.
  • DNA replication: The process of duplicating DNA.
  • Mitosis (cell cycle): DNA replication is vital for this process. Sister chromatids get separated during mitotic division. Important note: Homologous chromosomes don't pair in mitosis.
  • Meiosis: DNA replication occurs before meiosis, creating a reduction in chromosome number, that is, they are halved.
  • Prokaryotes (E. coli): Bacteria use DNA replication for binary fission.
  • Eukaryotes: Used in mitosis and meiosis.

DNA Replication in E. coli

  • Structure of OriC (E.coli): Circular DNA with specific sequences (ter 10 x 23-mers, A-J). These sequences create terminuses, or ends to the replication forks.
  • Initiation: DnaA, DnaC (helicase), and Gyrase proteins are crucial for initiating DNA replication.
  • Initiation Process: DnaC loads on the lagging strand, DnaB (helicase) follows, Gyrase is there to reduce torsional stresses of the DNA. DnaB (helicase) advances and DnaA displaces as a result.
  • Elongation: DNA polymerase III is the main enzyme for replication with RNA primers (roughly 10-60 nucleotides).
  • Okazaki fragments: Lagging strand synthesis is discontinuous, forming short fragments, which are later joined.
  • Continuous Synthesis (Leading Strand): Synthesis follows the replication fork in one direction.
  • Termination: This stops when the replication fork meets in the middle of the DNA, facilitated by proteins such as Tus, TerG, TerF, and so on.
  • Decatenation: Topoisomerase IV unwinds the entangled circular chromosomes into single circular DNA.
  • DNA replication video: Video links are provided for further understanding of the process.

DNA replication in Eukaryotes

  • Eukaryotic genomes are significantly larger than bacterial genomes.
  • Eukaryotes have a slower replication machinery than prokaryotes, and eukaryotes have linear chromosomes, unlike bacteria with circular chromosomes.
  • Cell cycle: The process the cell goes through, including DNA replication (during S phase), other phases, and more.

Telomeres

  • Telomeres are structures at the ends of linear chromosomes to prevent loss of genetic material, particularly during replication.

Differences between Prokaryotes and Eukaryotes

  • Prokaryotic DNA replication is usually faster and more simple, with fewer mechanisms involved, while eukaryotic replication is more complex due to longer genomes and linear nature of chromosomes.

Additional Slides

  • These slides provide further details and descriptions of the different processes and molecules involved.

Function of Gyrase in DNA Replication

  • Gyrase reduces torsional stresses in the DNA. A video link is included.

Cell Cycle (Eukaryotes)

  • The stages of the cell cycle (including DNA replication), and different phases of mitosis are explained with an illustration showing the stages in a circle.

Initiation (DNA Replication)

  • Initiation (starting) of DNA replication process is detailed, including specific proteins and steps.

S-phase Initiation

  • Cdc7 kinase and ORC (Origin Recognition Complex) proteins, as well as other related proteins, initiation of DNA replication.
  • Other proteins and steps involve further details and processes involved in DNA replication.

Replication Components

  • There are diagrams and descriptions of the components of the replication machinery (primosome, helicase, polymerases, etc.).

DNA Polymerase

  • The different kinds of DNA polymerase involved are discussed, along with their roles and the locations of these proteins and the reactions they catalyze.

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Related Documents

Part I-B: DNA Replication and Cell Cycle PDF

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