Histones and Nucleosomes in DNA Packaging
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Questions and Answers

What are the four types of core histone proteins found in a nucleosome?

  • H2A, H2B, H3, H4 (correct)
  • H1, H2, H3, H4
  • H2C, H2D, H3, H4
  • H2A, H3, H4, H5
  • How many histone proteins make up the core of a nucleosome?

  • 10
  • 6
  • 4
  • 8 (correct)
  • Which part of the nucleosome structure consists of DNA wrapped around a core of histone proteins?

  • Histone Core (correct)
  • Linker DNA
  • Nucleosome Unit
  • Chromatin
  • Where are nucleosomes particularly abundant in the eukaryotic genome?

    <p>Heterochromatic regions</p> Signup and view all the answers

    In approximately how many turns is the DNA double helix wound around the histone octamer in a nucleosome?

    <p>~1.65 turns</p> Signup and view all the answers

    What is the term that refers to the entire nucleosome structure including the core histones and the linker DNA segments?

    <p>Nucleosome Unit</p> Signup and view all the answers

    What is the most common ploidy in eukaryotic species?

    <p>2n</p> Signup and view all the answers

    Why is polyploidy rare in animals?

    <p>Lethal in animals</p> Signup and view all the answers

    Which organisms are more likely to exhibit polyploidy?

    <p>Plants and invertebrates</p> Signup and view all the answers

    How many chromosomes could be found in an allotriploid with species A having 2n = 20 and species B having 2n = 24?

    <p>34 or 32</p> Signup and view all the answers

    Why do some individuals mistakenly assume that a triploid has three times as many chromosomes as a normal individual?

    <p>Misunderstanding of basic genetics principles</p> Signup and view all the answers

    How is autotriploid chromosome number calculated?

    <p>(2n) * 3</p> Signup and view all the answers

    What would be the expected pattern of DNA density distribution in the Meselson-Stahl experiment if dispersive replication were correct?

    <p>A gradual shift towards lighter densities with each successive round of replication.</p> Signup and view all the answers

    Why would dispersive replication result in a diffuse band or smear on the density gradient in the Meselson-Stahl experiment?

    <p>Due to the fragmentation of parental DNA strands into smaller pieces.</p> Signup and view all the answers

    How does rolling circle replication compare to theta replication in terms of speed?

    <p>Rolling circle replication is typically faster for the same genome size and replication speed.</p> Signup and view all the answers

    In dispersive replication, what happens to the proportion of newly synthesized DNA with each round of replication?

    <p>It increases relative to parental DNA.</p> Signup and view all the answers

    What would the distribution of DNA densities reflect over successive rounds of dispersive replication?

    <p>The mixing of parental and newly synthesized DNA fragments.</p> Signup and view all the answers

    Why would rolling circle replication be faster than theta replication for the same genome size?

    <p>Due to the continuous synthesis of new DNA strands ahead of the replication fork.</p> Signup and view all the answers

    What is the main difference between theta replication and rolling circle replication?

    <p>Theta replication involves bidirectional DNA synthesis while rolling circle replication involves unidirectional synthesis.</p> Signup and view all the answers

    Which statement best describes the process of theta replication?

    <p>The DNA opens at the origin of replication and new strands are synthesized simultaneously at each fork.</p> Signup and view all the answers

    What are the main components of a nucleosome?

    <p>Histone Proteins: H2A, H2B, H3, H4</p> Signup and view all the answers

    How does the replication speed of rolling circle replication compare to theta replication?

    <p>Rolling circle replication is generally faster than theta replication.</p> Signup and view all the answers

    What role do histone proteins play in a nucleosome?

    <p>Histone proteins are the components around which DNA wraps to form a nucleosome.</p> Signup and view all the answers

    Why does rolling circle replication tend to proceed more rapidly than theta replication?

    <p>Because rolling circle replication does not require coordination of multiple forks, making it simpler and continuous.</p> Signup and view all the answers

    What is the main difference between euchromatin and heterochromatin?

    <p>Euchromatin is transcriptionally active, while heterochromatin is transcriptionally inactive.</p> Signup and view all the answers

    How does nucleosome structure contribute to the packaging of DNA?

    <p>Nucleosomes consist of DNA wrapped around a core of histone proteins, organizing long DNA strands.</p> Signup and view all the answers

    In which part of the nucleus is heterochromatin typically found?

    <p>At the periphery of the nucleus</p> Signup and view all the answers

    What contributes to the dynamic change between euchromatin and heterochromatin during the cell cycle?

    <p>Modifications to histone proteins and DNA methylation</p> Signup and view all the answers

    Why are genes within heterochromatic regions typically silenced or expressed at lower levels?

    <p>&quot; Due to the condensed nature and transcriptional inactivity of heterochromatin</p> Signup and view all the answers

    What role do nucleosomes play in chromosome organization?

    <p>&quot; Nucleosomes are involved in packaging and organizing long DNA strands</p> Signup and view all the answers

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