Biology Chapter: DNA Transformation Experiments
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Questions and Answers

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

  • To synthesize RNA from DNA templates
  • To coordinate the synthesis of leading and lagging strands (correct)
  • To copy DNA into proteins
  • To prevent mutations during DNA replication

    • In which direction does the replisome move during DNA replication?

  • Can move in either direction depending on the strand
  • Opposite to the direction of the fork
  • It does not move; it remains stationary
  • In the direction of the fork (correct)

    • What mechanism does the replisome utilize to synthesize the lagging strand?

  • Stranding using RNA primers only
  • A looping mechanism (correct)
  • Multiple enzymes acting independently
  • Continuous synthesis of nucleotides

    • What is the role of DNA polymerase in DNA replication?

    <p>To proofread and correct errors in nucleotide sequences</p> Signup and view all the answers

    What type of DNA damage can the repair mechanism specifically mentioned address?

    <p>Bulky DNA damage from radiation and mutagens</p> Signup and view all the answers

    What effect does histone methylation have on chromatin structure?

    <p>Tighter chromatin packaging</p> Signup and view all the answers

    Why can't polymerase add nucleotides directly to the 5' end of a DNA strand?

    <p>It has phosphate groups that are too electronically dense</p> Signup and view all the answers

    What is the primary effect of epigenetics in relation to gene expression?

    <p>Silences gene expression through chemical modifications</p> Signup and view all the answers

    In which direction do polymerases read the DNA during transcription?

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

    What structural charge do histones possess?

    <p>Positively charged</p> Signup and view all the answers

    What is the primary function of helicase in DNA replication?

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

    Which enzyme catalyzes the elongation of the DNA chain during replication?

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

    What is needed by DNA polymerase to begin synthesizing a new DNA strand?

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

    What type of bond is formed between nucleotides during DNA replication?

    <p>Phosphodiester bond</p> Signup and view all the answers

    In which direction does DNA elongation occur?

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

    What is released when a nucleotide is added to the growing DNA strand?

    <p>Two phosphate groups</p> Signup and view all the answers

    What role do single-stranded binding proteins play during DNA replication?

    <p>They hold DNA strands apart</p> Signup and view all the answers

    What component contributes to the energy necessary for forming new nucleotides during DNA synthesis?

    <p>Phosphate groups</p> Signup and view all the answers

    What does the intermediate density of DNA after one round of replication indicate?

    <p>Each new DNA molecule contains one strand from the original heavy DNA.</p> Signup and view all the answers

    What protein complex recognizes the origins of replication in eukaryotic chromosomes?

    <p>Origin Recognition Complex (ORC)</p> Signup and view all the answers

    How do eukaryotic chromosomes differ from prokaryotic ones regarding DNA replication?

    <p>Eukaryotic chromosomes have multiple origins of replication.</p> Signup and view all the answers

    What role do helicases play in DNA replication?

    <p>They unwind the DNA double helix.</p> Signup and view all the answers

    What does the semi-conservative model of DNA replication state?

    <p>Each new DNA molecule contains one original and one new strand.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of eukaryotic replication?

    <p>Replication occurs in a single cellular compartment.</p> Signup and view all the answers

    What is the effect of having multiple origins of replication in eukaryotic chromosomes?

    <p>Ability to replicate large genomes efficiently.</p> Signup and view all the answers

    During DNA replication, which proteins are recruited by the Origin Recognition Complex (ORC)?

    <p>Helicases and polymerases.</p> Signup and view all the answers

    What is the primary role of telomerase in cells?

    <p>To add DNA to telomeres</p> Signup and view all the answers

    What is the result of sequence changes in nucleotides?

    <p>They may result in mutations that can be passed to the next generation.</p> Signup and view all the answers

    Which type of chromatin is typically found at the centromeres and telomeres?

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

    How does euchromatin differ from heterochromatin?

    <p>Euchromatin is less condensed and more accessible to RNA polymerase.</p> Signup and view all the answers

    Why is an RNA primer necessary for DNA synthesis?

    <p>RNA primers provide a free 3' hydroxyl group for DNA polymerase.</p> Signup and view all the answers

    What issue arises at the end of the chromosome during DNA replication?

    <p>A shortage of RNA primers leads to overhanging DNA.</p> Signup and view all the answers

    What are nucleosomes composed of?

    <p>DNA wrapped around histone proteins</p> Signup and view all the answers

    What is the state of heterochromatin in relation to transcription?

    <p>It is transcriptionally silent.</p> Signup and view all the answers

    What is the role of telomeres in eukaryotic DNA?

    <p>They postpone the erosion of genes near the chromosome ends.</p> Signup and view all the answers

    What happens to the DNA during the action of telomerase?

    <p>Repeated sequences are added to the ends.</p> Signup and view all the answers

    What would potentially happen if germ cell chromosomes continue to shorten?

    <p>Essential genes could be lost in the gametes.</p> Signup and view all the answers

    What is the main characteristic of euchromatin?

    <p>It is accessible for transcription.</p> Signup and view all the answers

    How does the End Replication Problem affect cellular lifespan?

    <p>It may lead to cell death due to DNA shortening.</p> Signup and view all the answers

    What enzyme is responsible for lengthening telomeres in germ cells?

    <p>Telomerase.</p> Signup and view all the answers

    What is the primary function of heterochromatin during cell division?

    <p>It plays a role in chromosome segregation.</p> Signup and view all the answers

    What can potentially occur due to the absence of telomeres during replication?

    <p>Essential genes may erode in subsequent generations.</p> Signup and view all the answers

    Study Notes

    Frederick Griffith's Experiment

    • Griffith's experiment demonstrated transformation
    • R and S strains of Streptococcus pneumoniae were used
    • S strain (smooth) has a polysaccharide capsule
    • R strain (rough) lacks a capsule
    • Injecting heat-killed S strain with R strain transformed the R strain into S
    • This showed that some factor from the heat-killed S strain could change the R strain

    Oswald Avery and Maclyn McCarty's Experiment

    • Avery, MacLeod, and McCarty extended Griffith's work
    • They identified the transforming factor
    • Found that heat-killed S bacteria could only transform if their DNA remained intact
    • This confirmed DNA as the genetic material

    Viral DNA Programming Cells

    • Viruses inject DNA into host cells
    • Phage DNA hijacks host cell machinery to replicate phage DNA
    • The host cell then produces proteins and more phage particles
    • These new particles lyse (burst) the host cell, releasing more viruses

    What Did Chargaff Do?

    • Chargaff analyzed DNA from various organisms
    • Discovered consistent base ratios
    • C and G had equal ratios—A and T had equal ratios

    Semi-conservative Replication

    • DNA replication is semi-conservative
    • Each new DNA molecule is composed of one old strand and one new strand
    • The two strands separate, and each serves as a template for a new strand

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    Chapter 16 PDF

    Description

    Explore the key experiments that shaped our understanding of DNA and genetic transformation. From Griffith's initial discovery of transformation to Avery, MacLeod, and McCarty's identification of DNA as the transforming factor, this quiz covers crucial milestones in molecular biology. Additionally, delve into the role of viral DNA in cellular processes.

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