Chromatin and Epigenetics Overview
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Questions and Answers

What is disrupted when cells cannot load RAD51 onto ssDNA?

  • Branch migration
  • Single-strand annealing
  • Non-homologous end joining
  • Homologous recombination (correct)

    • Cells rely solely on homologous recombination for repair when RAD51 cannot load onto ssDNA.

    False

    What error-prone repair mechanism do cells rely on when homologous recombination is disrupted?

    Non-homologous end joining (NHEJ)

    When RAD51 cannot load onto ssDNA, cells might employ __________ to repair DNA.

    <p>error-prone repair mechanisms</p> Signup and view all the answers

    Match each DNA repair mechanism with its description:

    <p>NHEJ = Error-prone repair mechanism Homologous recombination = Accurate repair pathway SSA = Single-strand annealing method</p> Signup and view all the answers

    Which of the following statements is true regarding ssDNA and RAD51?

    <p>RAD51 loading onto ssDNA promotes homologous recombination.</p> Signup and view all the answers

    Single-strand annealing (SSA) is a reliable method for repairing DNA without errors.

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

    Name a repair mechanism that involves the joining of broken DNA ends without the need for homologous sequences.

    <p>Non-homologous end joining (NHEJ)</p> Signup and view all the answers

    Cells experiencing disruptions in homologous recombination often rely on __________ for DNA repair.

    <p>error-prone mechanisms</p> Signup and view all the answers

    Match the following repair mechanisms with their characteristics:

    <p>NHEJ = Repairs DNA by directly joining ends SSA = Involves homologous sequences Homologous recombination = Uses a template for accurate repair</p> Signup and view all the answers

    What is the core structure of a nucleosome composed of?

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

    H2AX is involved in gene expression.

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

    What is the function of the SWI/SNF complex?

    <p>Makes DNA accessible for transcription</p> Signup and view all the answers

    The ___ complex helps to disassemble and reassemble nucleosomes during transcription.

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

    Match the following histone variants to their functions:

    <p>H2AX = DNA repair and recombination H2AZ = Gene expression and chromosome segregation macroH2A = Transcriptional repression H3.3 = Transcriptional activation</p> Signup and view all the answers

    Which of the following enzymes is NOT involved in bacterial recombination?

    <p>RAD51</p> Signup and view all the answers

    CENP-A is a variant of H3 that plays a role in centromere function.

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

    Name one function of the INO80 complex.

    <p>Nucleosome sliding or DNA damage repair</p> Signup and view all the answers

    ___ complexes are crucial for regulating chromatin structure in response to specific histone modifications.

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

    Which of the following is a function of the RuvB enzyme?

    <p>Involved in branch migration during recombination</p> Signup and view all the answers

    Study Notes

    Chromatin and Epigenetics

    • Nucleosomes are composed of H2A, H2B, H3, and H4 proteins
    • H3 and H4 dimers combine to form tetramers
    • Tetramers bind two H2A-H2B dimers forming an octamer
    • 147 base pairs (bp) of DNA are wrapped around an octamer
    • DNA linker regions are 38-53 bp long
    • Histone variants, such as H2A.Z and H2AX, have specific functions
      • H2AX is involved in DNA repair
      • H2A.Z aids in gene expression
    • Histone variants like macroH2A are involved in transcriptional repression

    Remodeling Complexes

    • SWI/SNF complex alters nucleosome structure
    • Crucial for DNA accessibility for transcription
    • Slides and ejects nucleosomes
    • Second most mutated gene family across various cancers
    • INO80 complex is another remodeling complex, involved in nucleosome sliding
    • Crucial in histone exchange/replacement, particularly H2A.Z, essential for transcription
    • Important in DNA damage repair, makes damaged DNA accessible to repair machinery
    • Plays a key role in replication stress response by stabilizing replication forks and preventing stress
    • Any condition that slows or disrupts replication is countered by stress response

    Genetic Recombination

    • Enzymes play vital roles in bacterial/eukaryotic recombination
    • Enzymes like RecA, RecB, RecC, RecD, RuvC, RuvA, RuvB, RecG, RAD50, XRS2, MRE11, Sae2, Tel1, RAD51, RAD52, and BRAC2 play crucial roles in the process
    • Some functions across different systems (bacterial or eukaryotic)
    • Holliday junctions are key structures during recombination.
    • Branch migration is a critical step during recombination. Mechanisms in eukaryotes include:
      • Non-homologous end joining (NHEJ)
      • Single-strand annealing (SSA)

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    Description

    This quiz covers the essential concepts of chromatin structure and the role of epigenetics. It includes details about nucleosomes, histone variants, and the function of remodeling complexes like SWI/SNF and INO80. Test your knowledge on how these components contribute to DNA accessibility and gene regulation.

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