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The Epigenetic Code quiz

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  • What is chromatin composed of?
    Chromatin is composed of DNA and proteins, mainly histone proteins.
  • What are the two forms of chromatin and how do they differ?
    The two forms are euchromatin (less condensed, allowing gene expression) and heterochromatin (more condensed, generally repressing gene expression).
  • Why are genes in heterochromatin usually not expressed?
    Genes in heterochromatin are not expressed because the DNA is tightly packed, preventing access by transcription factors and other proteins.
  • What is the position effect in relation to gene expression?
    Position effect refers to the decreased expression of genes located near heterochromatin due to their proximity to condensed, silent regions.
  • What role do histone proteins play in chromatin structure?
    Histone proteins package and condense DNA, forming nucleosomes and influencing chromatin structure.
  • What are the two most common histone modifications and their effects?
    Acetylation loosens chromatin structure, while methylation tightens it, affecting gene accessibility.
  • How does acetylation affect chromatin and gene expression?
    Acetylation removes positive charges from histones, loosening chromatin and making genes more accessible for expression.
  • What is the effect of methylation on chromatin structure?
    Methylation tightens chromatin structure, often repressing gene expression and preventing acetylation.
  • What is a chain reaction in histone modification?
    A chain reaction occurs when one histone modification triggers similar modifications along a stretch of amino acids, affecting large regions of chromatin.
  • What prevents unlimited spread of histone modifications?
    Barrier sequences stop the chain reaction of histone modifications, separating condensed and non-condensed chromatin regions.
  • What is the epigenetic code?
    The epigenetic code is the pattern of histone modifications that dynamically regulate gene expression, DNA replication, and cell division.
  • How do chromatin remodeling complexes influence gene expression?
    Chromatin remodeling complexes use ATP to reposition DNA within nucleosomes, allowing or restricting access to specific DNA regions.
  • What is epigenetic inheritance?
    Epigenetic inheritance is the transmission of chromatin states and histone modifications across cell divisions and potentially to offspring.
  • How does epigenetic inheritance contribute to cellular memory?
    Epigenetic inheritance allows cells to retain chromatin states and histone modifications, enabling non-genetic cellular memory.
  • What is the significance of nucleosome movement in the epigenetic code?
    Nucleosome movement, controlled by remodeling complexes, exposes or hides DNA regions, affecting gene expression and replication.