Molecular Biology: DNA Replication Quiz
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Questions and Answers

What is the main function of RNA primase during DNA replication?

  • To extend the new DNA strands
  • To remove DNA primers and replace them with DNA
  • To join Okazaki fragments
  • To lay down an RNA primer for DNA polymerase (correct)

What differentiates the template for the leading strand from the lagging strand during DNA replication?

  • The leading strand is synthesized discontinuously, while the lagging strand is continuous.
  • The leading strand is read continuously in a 3' to 5' direction, while the lagging strand is read in the same direction, but discontinuously. (correct)
  • The leading strand synthesizes Okazaki fragments, unlike the lagging strand.
  • The leading strand requires multiple primers, unlike the lagging strand.

What role does DNA ligase play in the process of DNA replication?

  • It removes RNA primers and replaces them with DNA.
  • It joins nicks between DNA fragments. (correct)
  • It acts as a template for DNA polymerase.
  • It synthesizes Okazaki fragments.

What characteristic is notable about telomeres in eukaryotic chromosomes?

<p>They protect chromosomes from unraveling and buffer against loss of replication. (B)</p> Signup and view all the answers

Which of the following statements about DNA polymerase I and III is correct?

<p>DNA polymerase I removes RNA primers, while DNA polymerase III extends the new DNA strands. (A)</p> Signup and view all the answers

What is the correct model of DNA replication that was concluded by Meselson and Stahl?

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

Which enzyme is responsible for linking new nucleotides during DNA replication?

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

Which of the following statements about the structure of DNA is incorrect?

<p>A binds with C and T with G. (A)</p> Signup and view all the answers

During DNA replication, in which direction does the new strand grow?

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

What is released during the nucleotide linkage process in DNA replication?

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

What role do regulatory proteins play in DNA structure?

<p>They determine whether a gene is active or inactive. (A)</p> Signup and view all the answers

What is the function of DNA helicase during DNA replication?

<p>To separate the two DNA strands. (A)</p> Signup and view all the answers

Which part of the nucleotide acts as the energy source during DNA replication?

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

What was the main conclusion from Frederick Griffith's experiments regarding the genetic material?

<p>DNA is the transforming factor. (D)</p> Signup and view all the answers

Which strain of Streptococcus pneumoniae has a protective capsule?

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

What was the purpose of Avery et al.'s experiment in 1944?

<p>To identify whether DNA or protein was the transforming factor. (B)</p> Signup and view all the answers

In Griffith's experiment, what was observed after R cells took up genetic material from dead S cells?

<p>R cells became virulent. (D)</p> Signup and view all the answers

What does the term 'transforming factor' refer to in the context of Griffith's experiments?

<p>The DNA taken in by R cells from dead S cells. (D)</p> Signup and view all the answers

Why are telomeres important in DNA replication?

<p>They prevent the loss of important genetic information during replication. (C)</p> Signup and view all the answers

What role does DNA proofreading play in genetic fidelity?

<p>It checks and corrects errors during DNA replication. (D)</p> Signup and view all the answers

What is the primary purpose of DNA packaging in cells?

<p>To fit long DNA molecules into the cell nucleus. (B)</p> Signup and view all the answers

What causes telomere shortening during DNA replication?

<p>Non-replicated 3' ends of the lagging strand (B)</p> Signup and view all the answers

What is a key characteristic of Werner syndrome?

<p>It is caused by a mutation in the WRN protein. (C)</p> Signup and view all the answers

What was the main purpose of the Hershey-Chase experiment?

<p>To identify whether DNA or protein is the genetic material (B)</p> Signup and view all the answers

Which mechanism helps correct DNA replication errors as they occur?

<p>Proofreading mechanism of polymerase (D)</p> Signup and view all the answers

How does mismatch repair identify incorrect bases in DNA?

<p>By detecting non-methylated incorrect bases (B)</p> Signup and view all the answers

What conclusion resulted from the Hershey-Chase experiment regarding phage T2?

<p>DNA, not protein, is the genetic material of phage T2 (B)</p> Signup and view all the answers

According to Chargaff's rules, which nucleotide pairs occur in a 1:1 ratio?

<p>A with T and C with G (B)</p> Signup and view all the answers

What is the typical mutation rate in E. coli nucleotides?

<p>1 in 10^9 nucleotides (C)</p> Signup and view all the answers

What are the four primary functions of DNA mentioned in the content?

<p>Store info, replicate, express phenotype, and undergo mutations (C)</p> Signup and view all the answers

What role does oxidative stress play in aging?

<p>It causes damage to cellular DNA. (D)</p> Signup and view all the answers

What is the primary function of telomerase in cells?

<p>To elongate telomeres (D)</p> Signup and view all the answers

What structural discovery about DNA was made by Watson and Crick in 1953?

<p>DNA is a double helix (A)</p> Signup and view all the answers

Which of the following best describes the end replication problem?

<p>Incomplete replication of the 3' ends of the lagging strand (C)</p> Signup and view all the answers

What aspect of DNA contributes directly to its function in evolution?

<p>The sequence of nucleotides (B)</p> Signup and view all the answers

What role did Rosalind Franklin play in the discovery of DNA's structure?

<p>Her X-ray crystallography provided key insights (B)</p> Signup and view all the answers

Which of the following statements about the components of DNA is accurate prior to 1950?

<p>Nucleotides are made of sugar, phosphate, and a nucleotide base (D)</p> Signup and view all the answers

Flashcards

Transformation

The process where non-pathogenic bacteria become pathogenic by taking up genetic material from dead pathogenic bacteria.

S strain bacteria

A strain of bacteria that causes disease, in this case pneumonia, and is protected by a capsule.

R strain bacteria

A strain of bacteria that does not cause disease, and lacks a protective capsule.

Streptococcus pneumoniae

The bacteria used in Griffith's experiment, existing in two forms (S and R strains).

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Frederick Griffith

The scientist who discovered the transformation process in bacteria.

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Griffith's Experiment

The experiment that showed DNA can transform harmless bacteria into harmful ones.

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Avery et al.

The scientists who showed that DNA is the 'transforming' substance, not protein.

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DNA

The molecule identified as the transforming factor passed between bacterial cells that carries the genetic information

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Single-strand binding proteins

Proteins that stabilize single-stranded DNA during replication.

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RNA primase

An enzyme that synthesizes a short RNA sequence to initiate DNA replication.

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Leading strand

The DNA strand that is synthesized continuously during replication.

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Lagging strand

The DNA strand that is synthesized discontinuously in fragments.

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Telomeres

Repetitive sequences at the ends of chromosomes that protect them from degradation.

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Bacteriophage (T2 Phage)

A virus that infects bacteria; specifically, T2 phage is made of protein and DNA.

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Hershey-Chase Experiment

Experiment using radioactive isotopes to determine whether DNA or protein was the genetic material of T2 phage. Concluded DNA, not protein, functions as T2 phage’s genetic material.

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DNA Nucleotides

The building blocks of DNA, consisting of a sugar, phosphate, and a nitrogenous base (A, G, T, or C).

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Chargaff's Rules

The observation that the ratios of adenine (A) to thymine (T), and cytosine (C) to guanine (G) are equal in DNA.

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Base Sequence

The order of bases along the DNA molecule; encodes genetic information.

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DNA Replication

The ability of DNA to create exact copies of itself during cell division.

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Phenotype Expression

The process by which the information in DNA is used to make a functional product, such as RNA or proteins

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DNA Mutation

Changes in the DNA sequence, leading to genetic diversity; errors in replication or recombination.

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Antiparallel

DNA strands run in opposite directions to each other. One strand runs 5' to 3' and the other runs 3' to 5'.

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Right-handed helix

The DNA double helix twists to the right, forming a spiral shape.

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Regulatory proteins

Proteins that bind to DNA to control whether a gene is expressed or not.

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Semiconservative model

The model where each new DNA molecule contains one original strand and one new strand.

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Origins of replication

Specific locations on DNA where replication starts.

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DNA Helicase

The enzyme that separates the two DNA strands using ATP energy.

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Topoisomerase

Enzymes that relax supercoiled DNA during replication.

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Telomere end replication problem

The process where the lagging strand of DNA cannot be fully replicated at its 3’ end, causing telomere shortening over time.

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Oxidative stress

Chemical or mechanical damage to cells, including DNA, caused by reactive molecules like free radicals.

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Werner syndrome

A genetic disorder that causes accelerated aging, linked to a mutation in the WRN protein.

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Elizabeth Blackburn

A professor who won the Nobel Prize for her work on telomeres and telomerase.

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Proofreading mechanism of polymerase

A DNA repair mechanism where DNA polymerase corrects mistakes during DNA replication.

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Mismatch repair

A DNA repair mechanism that scans DNA after replication to fix mismatched base pairs. It uses methylation to identify the new (incorrect) strand

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Study Notes

DNA Structure and Replication

  • DNA is the genetic material of life.
  • DNA has a double helix structure.
  • DNA replication is a process where DNA makes a copy of itself.
  • DNA proofreading and repair mechanisms correct errors in replication and environmental damage.
  • Telomeres are the ends of eukaryotic chromosomes protecting them from loss of information.
  • Telomeres are rich in TTAGGG sequence (in humans).
  • Telomere shortening is an aging problem

DNA as Genetic Material

  • 1928, Frederick Griffith experimented with Streptococcus pneumoniae bacteria.
  • He used S (smooth) and R (rough) strains to show transformation.
  • This indicated that genetic material was transferred, possibly DNA.

Identifying the Transforming Substance

  • 1944, Avery et al. identified DNA as the transforming substance.
  • 1952, Hershey and Chase used bacteriophages to confirm DNA as genetic material.
  • They labeled phage DNA and proteins radioactively and traced DNA entry into bacterial cells.

DNA Structure

  • DNA is a double helix.
  • 1 turn is 3.4 nm.
  • Distance between adjacent nucleotides = 0.34 nm.
  • The structure suggests a replication method.
  • A pairs with T and C pairs with G.
  • DNA is a double helix with an antiparallel and right-handed orientation.

DNA Replication

  • The basic idea: one strand acts as a template for making a new strand.
  • Four requirements: template, complementary base-pairing, building blocks (dNTPs), and an enzyme (DNA polymerase).
  • DNA polymerase needs energy (phosphoanhydride bonds of dNTPs).
  • Three major steps of replication include denaturation, primer linking to start new strands and strand elongation (forming new strands).

Semiconservative Replication (Correct model)

  • Meselson and Stahl study used density gradient centrifugation to separate DNA based on 14N and 15N isotopes.
  • Their results supported the semiconservative model of replication.

DNA Proofreading and Repair

  • DNA is subject to errors of replication and environmental damage.
  • Replication is very fast in E. coli (1000 base pairs/second).
  • Proofreading and repair mechanism in DNA polymerase corrects errors as DNA is made .
  • Mismatch repair scans DNA to correct mismatches.
  • Excision repair removes UV or chemically damaged bases.

Packaging DNA

  • DNA is packaged with histone proteins.
  • Nucleosomes are formed (DNA wrapped around histone octamers).
  • 10-nm fiber, 30-nm fiber and 300-nm loop domains.
  • Chromosomes are ultimately formed.

Telomere End Replication Problem

  • The 3' end of the lagging strand template is not completely replicated because DNA polymerase can only add nucleotides to the 3' end.
  • Okazaki fragments are formed in lagging strand replication.

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Biology 135A DNA Structure and Replication PDF

Description

Test your knowledge on the processes and enzymes involved in DNA replication! This quiz covers key concepts such as the role of RNA primase, the function of DNA ligase, and the differences between leading and lagging strands. Challenge yourself with questions on nucleotide linkage and the structure of DNA.

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