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Eukaryotic Chromatin Modifications quiz #2

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  • What is chromatin?
    Chromatin is a complex of DNA and histone proteins that forms a structure in the nucleus of eukaryotic cells. It can be loosely packed (euchromatin) or tightly packed (heterochromatin), affecting gene expression.
  • What is the function of ATP-dependent chromatin-remodeling complexes?
    ATP-dependent chromatin-remodeling complexes use energy from ATP hydrolysis to alter chromatin structure, making DNA more or less accessible for transcription.
  • DNA methylation and histone acetylation are examples of which biological process?
    Epigenetic modifications. These processes modify gene expression without altering the DNA sequence.
  • What is heterochromatin?
    Heterochromatin is a tightly packed form of chromatin that is transcriptionally inactive, preventing gene expression.
  • What does the DNA methylation mechanism used by eukaryotes do?
    DNA methylation adds methyl groups to cytosine residues, typically silencing genes by blocking transcription.
  • What is the difference between euchromatin and heterochromatin?
    Euchromatin is loosely packed and transcriptionally active, while heterochromatin is tightly packed and transcriptionally inactive.
  • What is euchromatin?
    Euchromatin is a loosely packed form of chromatin that is transcriptionally active, allowing gene expression.
  • What is the difference between heterochromatin and euchromatin?
    Heterochromatin is tightly packed and transcriptionally inactive, while euchromatin is loosely packed and transcriptionally active.
  • What are the key functional roles of heterochromatin in eukaryotic cells?
    Heterochromatin plays roles in gene silencing, maintaining chromosome stability, and regulating gene expression.
  • What occurs in histone acetylation and how does it affect gene expression?
    Histone acetylation involves adding acetyl groups to histone tails, loosening chromatin structure and enhancing gene expression by making DNA more accessible.
  • What are examples of heterochromatin in eukaryotic cells?
    Centromeres, telomeres, and the inactive X chromosome are examples of heterochromatin.
  • Why are genes contained in compact chromatin not expressed?
    Genes in compact chromatin, or heterochromatin, are not expressed because the tightly packed structure prevents access by transcriptional machinery.
  • What effect can ATP-dependent chromatin remodeling have on transcription?
    ATP-dependent chromatin remodeling can either increase or decrease transcription by altering chromatin structure to make DNA more or less accessible.
  • What is a false statement about eukaryotic chromosomes regarding their transcriptional activity?
    Eukaryotic chromosomes can be transcriptionally inactive when in heterochromatin form.
  • What effect does methylation of CpG islands have on human promoters?
    Methylation of CpG islands typically silences human promoters by preventing transcription factor binding and blocking transcription.
  • Of the proteins associated with chromatin, which are primarily involved in chromatin structure and gene regulation?
    Histone proteins are primarily involved in chromatin structure and gene regulation through modifications like acetylation and methylation.
  • What is the role of DNA methylation in eukaryotes?
    DNA methylation in eukaryotes typically silences genes by adding methyl groups to cytosine residues, blocking transcription.
  • How do histone acetylation and DNA methylation affect gene expression in eukaryotic cells?
    Histone acetylation loosens chromatin structure, forming euchromatin and increasing gene transcription by making DNA accessible to RNA polymerase. DNA methylation adds methyl groups to cytosine residues, leading to chromatin condensation (heterochromatin) and gene silencing by blocking RNA polymerase access.