Molecular Biology - DNA Replication
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Questions and Answers

What connects the 5' carbon atom of one deoxyribose sugar to the 3' carbon atom of another nucleotide?

  • A phosphoester bond
  • An ionic bond
  • A hydrogen bond
  • A covalent bond (correct)

Which end of the DNA molecule is responsible for the addition of new nucleotides?

  • 5' and 3' ends are identical
  • Neither end allows for addition
  • 3' end (correct)
  • 5' end

What is released when a diphosphate molecule is split off during the addition of a nucleotide?

  • Energy (correct)
  • Heat energy
  • Carbon dioxide
  • Oxygen

Which of the following is a distinguishing feature of RNA compared to DNA?

<p>Single-stranded structure (A)</p> Signup and view all the answers

What is the significance of the hydroxyl group at the 3' end of a nucleotide in DNA?

<p>It allows for the addition of more nucleotides (B)</p> Signup and view all the answers

What area does molecular biology primarily focus on?

<p>Biological processes in terms of molecular interactions (A)</p> Signup and view all the answers

Which components are important in DNA replication?

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

What is the primary focus of genetics within molecular biology?

<p>Understanding the inheritance and characterization of gene products (A)</p> Signup and view all the answers

Who coined the term 'molecular biology'?

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

Which of the following best describes biochemistry?

<p>Investigation of macromolecules' structures and actions (A)</p> Signup and view all the answers

How does DNA replication differ between eukaryotes and prokaryotes?

<p>Eukaryotes utilize a complex of enzymes for replication (C)</p> Signup and view all the answers

What is the primary contribution of cell biology to molecular biology?

<p>Studying the structural functions of cell organelles (B)</p> Signup and view all the answers

Which scientific disciplines contribute to the field of molecular biology?

<p>Cell biology, genetics, and biochemistry (C)</p> Signup and view all the answers

Which of the following nitrogenous bases is classified as a purine?

<p>Adenine (D)</p> Signup and view all the answers

What distinguishes nucleotides from nucleosides?

<p>Nucleotides contain a phosphate group. (C)</p> Signup and view all the answers

Which sugar is present in ribonucleic acid (RNA)?

<p>β-D-ribose (A)</p> Signup and view all the answers

How are nucleosides formed?

<p>By linking a nitrogenous base to the 1' carbon of a sugar. (A)</p> Signup and view all the answers

Which of the following statements is true about uracil?

<p>It replaces thymine in RNA. (D)</p> Signup and view all the answers

What are the structural components of a nucleotide?

<p>Phosphate group, nitrogenous base, and sugar. (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic of nucleotides?

<p>They lack a nitrogenous base. (A)</p> Signup and view all the answers

What are purines and pyrimidines based on?

<p>Their ring structures. (C)</p> Signup and view all the answers

What is the main role of telomerase in DNA replication?

<p>To extend the ends of chromosomes (C)</p> Signup and view all the answers

What characterizes the semi-conservative model of DNA replication?

<p>Each daughter DNA contains one parental strand and one newly synthesized strand (B)</p> Signup and view all the answers

Which enzyme is responsible for replacing RNA primers with DNA nucleotides?

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

Which of the following models allows both strands of DNA to remain unchanged?

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

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

<p>To ensure DNA polymerase remains attached (C)</p> Signup and view all the answers

What is the replication speed of the DNA polymerase?

<p>1000 nucleotides/s (C)</p> Signup and view all the answers

Which polymerase is involved in strand elongation during DNA replication?

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

How does the location of RNA primers affect the ends of chromosomes during replication?

<p>The ends cannot be extended without a primer (C)</p> Signup and view all the answers

Which enzyme is responsible for removing RNA primers during DNA replication?

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

During DNA replication in eukaryotes, where does the replication take place?

<p>In the cell nucleus (A)</p> Signup and view all the answers

What aspect of replication is described as semi-conservative?

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

What structure serves as a template for the extension of the problematic DNA strand in telomere replication?

<p>Telomerase RNA Component (A)</p> Signup and view all the answers

In eukaryotic DNA replication, what process occurs after the RNA primer is removed?

<p>DNA ligase joins Okazaki fragments and closes nicks in the DNA. (D)</p> Signup and view all the answers

What is the significance of multiple origins of replication in eukaryotic cells?

<p>It allows for faster replication of the entire genome. (C)</p> Signup and view all the answers

Which statement best describes the termination process of DNA replication in eukaryotes?

<p>It allows for the extension of one of the strands using telomerase. (B)</p> Signup and view all the answers

What is the role of primase in DNA replication?

<p>It synthesizes a short strand of RNA to provide a primer. (C)</p> Signup and view all the answers

How are the leading and lagging strands synthesized during DNA replication?

<p>The leading strand is synthesized continuously while the lagging strand is synthesized in short fragments. (C)</p> Signup and view all the answers

What is the function of DNA ligase in DNA replication?

<p>To seal the breaks between Okazaki fragments after synthesis. (D)</p> Signup and view all the answers

In which direction does DNA polymerase synthesize DNA?

<p>5'→3' direction for the leading strand and 5'→3' direction for the lagging strand in fragments. (A)</p> Signup and view all the answers

What initiates the process of DNA synthesis by DNA polymerase?

<p>The annealing of a primer to the template strand. (A)</p> Signup and view all the answers

Flashcards

DNA Nucleotide Bonds

Nucleotide monomers in DNA are connected by covalent bonds between the sugar of one nucleotide and the phosphate of the next.

DNA 5' and 3' ends

The DNA strand has distinct ends: the 5' end has a phosphate group, and the 3' end has a hydroxyl group. New nucleotides are always added to the 3' end.

DNA Growth Direction

DNA grows by adding nucleotides to the 3' end of the existing strand.

RNA vs. DNA Thymine

RNA replaces the Thymine base in DNA with Uracil.

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RNA Sugar

RNA uses ribose sugar instead of deoxyribose.

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Molecular Biology definition

Explains biological processes through molecular interactions, often described as the biochemistry of genes and their products.

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Genetics role in Molecular Biology

Focuses on identifying and characterizing gene products and patterns of inheritance.

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Cell Biology role in Molecular Biology

Examines the structure and function of cells and their organelles.

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Biochemistry role in Molecular Biology

Involves understanding the 3D structures and actions of biological molecules (macromolecules).

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Coining of Molecular Biology term

Coined by Warren Weaver in 1938, a Rockefeller Foundation director.

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DNA Replication components

Important components involved in DNA replication such as enzymes and raw materials.

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DNA Replication mechanism

The method in which DNA replicates, involving different steps and processes.

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DNA Replication difference - eukaryotes vs. prokaryotes

Describes the distinctions in DNA replication mechanisms between eukaryotic and prokaryotic organisms.

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Purines

A class of nitrogenous bases that include adenine and guanine.

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Pyrimidines

A class of nitrogenous bases that include cytosine, thymine, and uracil.

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Nucleotide components

A phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogenous base form a nucleotide.

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Nucleoside

A nitrogenous base bonded to a pentose sugar.

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RNA

Ribonucleic acid; a type of nucleic acid composed of ribonucleotides.

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DNA

Deoxyribonucleic acid; a type of nucleic acid composed of deoxyribonucleotides.

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Nitrogenous bases in nucleic acids

Adenine, Guanine, Cytosine, Thymine (in DNA), and Uracil (in RNA).

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Nucleotides vs. nucleosides

Nucleotides include a phosphate group; nucleosides do not.

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What is the role of single-stranded binding protein in DNA replication?

Single-stranded binding protein (SSB) prevents the separated DNA strands from re-annealing during replication, ensuring the template strands remain accessible for new nucleotide pairing.

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Why is a primer needed for DNA replication?

DNA polymerase, the enzyme responsible for synthesizing new DNA, can only add nucleotides to an existing 3' hydroxyl group. A primer, typically a short RNA sequence, provides this initiation point for DNA polymerase to start building the new strand.

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Leading strand vs. lagging strand

The leading strand is synthesized continuously in the 5' to 3' direction, following the movement of the replication fork. The lagging strand is synthesized discontinuously in short fragments (Okazaki fragments) because its orientation is opposite to the fork's movement.

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What does DNA polymerase I do in DNA replication?

DNA polymerase I removes the RNA primers from the Okazaki fragments on the lagging strand and replaces them with DNA nucleotides. This ensures continuity of the newly synthesized DNA.

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What is the function of DNA ligase in DNA replication?

DNA ligase seals the gaps between the Okazaki fragments on the lagging strand, joining them into a continuous DNA molecule. This final step ensures the integrity of the newly replicated DNA.

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What are the 3 DNA replication models?

The three models are semi-conservative, conservative, and dispersive. Each model proposes a different way DNA duplicates itself during replication.

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Semi-conservative replication

This model suggests that each strand of the DNA molecule separates, and each serves as a template for a new complementary strand. The resulting daughter DNA molecules have one parent strand and one newly synthesized strand.

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Conservative replication

This model proposes that both strands of the DNA duplex are replicated entirely, generating two completely new strands that pair together. Meanwhile, the original strands remain paired together.

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Dispersive Replication

This model suggests that the parental DNA is broken into fragments, and each fragment serves as a template for a new strand. The resulting daughter DNA molecules contain a mixture of parental and newly synthesized DNA segments.

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Why is DNA replication semi-conservative?

DNA replication is semi-conservative because one strand is the original (conserved) and one strand is freshly assembled (semi-half).

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Template strand

This is the existing DNA strand that serves as a guide for the synthesis of a new complementary strand during DNA replication.

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Daughter DNA

The resulting DNA molecules after replication, each consisting of one parental strand and one newly synthesized strand.

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Base pairing in DNA replication

The process where complementary bases, adenine (A) with thymine (T) and guanine (G) with cytosine (C), bind together during DNA replication, ensuring accurate copying of the genetic information.

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Telomere Dilemma

The problem of shortening DNA strands during replication due to primers on the lagging strand, which DNA polymerase I can't replace.

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Telomerase Enzyme

A ribonucleoprotein enzyme that extends the length of one DNA strand during replication by adding repeated sequences to the 3' end. This prevents chromosomes from shortening.

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Telomerase Reverse Transcriptase (TERT)

The protein component of telomerase that has reverse transcriptase activity, meaning it can use RNA as a template to synthesize DNA.

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Primer Removal in Termination

DNA polymerase I removes RNA primers from Okazaki fragments on the lagging strand and replaces them with DNA nucleotides.

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DNA Ligase Function

DNA ligase joins Okazaki fragments together to form a continuous DNA strand, sealing the gaps between them.

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Multiple Origins of Replication

Eukaryotic DNA replication originates at various points on the chromosome (Ori C) instead of a single starting point, allowing faster replication.

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S Phase Replication

DNA replication occurs exclusively in the S phase (synthesis phase) of the cell cycle, ensuring accurate copying of the genome before cell division.

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Study Notes

Molecular Biology - Replication

  • Molecular biology is the study of biological processes in terms of molecular interactions. It combines biochemistry, genetics, and cell biology.
  • DNA replication is a fundamental process, ensuring identical copies of DNA for inheritance.
  • Replication begins at specific points called origins of replication and proceeds bidirectionally, or in one direction.
  • Replication requires an unwinding and separation of the original double-stranded DNA template. Each original strand acts as a template for building the new strand.
  • The DNA replicates semi-conservatively, meaning each new DNA molecule contains one original (parental DNA) strand and one newly synthesized strand, ensuring genetic continuity.
  • DNA replication involves multiple enzymes and other proteins, some are involved in the unwinding of the DNA helix, others in ensuring the accuracy of the copy.
  • A specialized enzyme, DNA polymerase III, synthesizes new DNA strands in a 5' to 3' direction.
  • Okazaki fragments are short DNA pieces synthesized on the lagging strand, which is the strand synthesized discontinuously in the 3' to 5' direction. These fragments are then joined by DNA ligase to complete the new strand.
  • Initiation, elongation, and termination are the three primary phases of DNA replication.

DNA Replication - Steps

  • Initiation: Replication begins at specific origins of replication, where DNA helicases unwind and separate the DNA double helix. Single-stranded DNA binding proteins (SSBs) prevent the separated strands from re-annealing. Topoisomerases alleviate the torsional stress caused by unwinding.
  • Elongation: DNA polymerase III adds nucleotides to the 3' end of the RNA primers, synthesizing new DNA strands in the 5' to 3' direction. The leading strand is created continuously, while the lagging strand is produced in short fragments called Okazaki fragments. These fragments are later joined by DNA ligase.
  • Termination: Replication continues until the entire chromosome is replicated. The ends of linear chromosomes (telomeres) present a unique problem, as DNA polymerases cannot replicate the very ends of the lagging strand. Telomerase, an enzyme, extends these ends to prevent chromosomal shortening. Another enzyme, DNA Polymerase I, replaces RNA primers with DNA. DNA ligase joins Okazaki fragments.

DNA Replication - Enzymes

  • DNA helicase: Unwinds the DNA double helix, making the template strands available.
  • Single-strand binding proteins (SSBs): Prevent the separated DNA strands from re-annealing.
  • DNA topoisomerase (DNA gyrase): Alleviates torsional stress, which is a common effect of unwinding the helix.
  • DNA polymerase III: Adds nucleotides to the 3' end of the template strand.
  • DNA polymerase I: Removes RNA primers and replaces them with DNA.
  • DNA ligase: Joins Okazaki fragments on the lagging strand.
  • Primase: Synthesizes short RNA primers (initial segments) at the origin of replication.
  • Telomerase: Adds telomeric sequences to the ends of linear chromosomes, preventing shortening.

Common Terms in Molecular Biology

  • Gene: A segment of DNA that codes for a specific protein.
  • Chromosome: A structure composed of DNA that carries genetic information.
  • Genome: The complete set of genetic information in an organism, including all its genes.
  • Genomics: The study of the entirety of an organisms's genetic material.
  • Genotype: The genetic makeup of an organism (alleles).
  • Phenotype: The observable physical and behavioral traits of an organism, caused by the interplay between genes and environmental influences.

Additional Information

  • The process differs slightly in prokaryotes (bacteria) and eukaryotes (animal and plant cells). For example, eukaryotes have multiple origins of replication.
  • DNA replication is essential for cell growth and reproduction, and is fundamental to all living organisms.

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Replication PDF - Lecture Notes

Description

Explore the critical process of DNA replication in molecular biology. This quiz covers the mechanisms, key enzymes involved, and the semi-conservative nature of DNA synthesis. Test your knowledge on how genetic continuity is maintained through accurate replication.

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