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Soru

Zorluk: OrtaCell Biology, Genetics, and Evolution

In eukaryotic cells, genomic DNA undergoes progressive compaction with structural proteins to form chromatin. Which of the following statements regarding the molecular organization of nucleosomes and chromatin architecture are correct?

  1. A canonical nucleosome core particle consists of approximately 146 to 147 base pairs of DNA wrapped around an octamer composed of two molecules each of histones H2AH2A, H2BH2B, H3H3, and H4H4.Cevap
  2. Euchromatin represents a loosely packed, transcriptionally active state of chromatin that stains lightly under standard microscopic staining during interphase.Cevap
  3. C
    Heterochromatin is a highly condensed, transcriptionally hyperactive chromatin state characterized by pervasive core histone hyperacetylation.
  4. D
    Linker histone H1H1 forms the central core of the nucleosome octamer and permanently represses DNA replication across all somatic cells.

Cevap

The statements describing the nucleosome core structure (composed of DNA wrapped around a histone octamer of H2AH2A, H2BH2B, H3H3, and H4H4) and identifying euchromatin as loosely packed, transcriptionally active chromatin are correct.
The statements describing the canonical nucleosome core particle (146–147 bp146\text{--}147\text{ bp} DNA wrapped around an octamer of H2AH2A, H2BH2B, H3H3, and H4H4) and characterizing euchromatin as transcriptionally active, loosely condensed chromatin are accurate biological facts.

Adım Adım Çözüm

1
Analyze the structural composition of the core nucleosome particle.
Confirm that the nucleosome core comprises ≈146–147 bp\approx 146\text{--}147\text{ bp} of DNA wrapped around a histone octamer consisting of pairs of H2AH2A, H2BH2B, H3H3, and H4H4.
This represents the fundamental repeating structural unit of eukaryotic chromatin.
2
Evaluate the functional and staining properties of euchromatin versus heterochromatin.
Identify euchromatin as lightly staining, relaxed, and transcriptionally active, whereas heterochromatin is densely packed, darkly staining, and transcriptionally repressed.
Chromatin remodeling and histone modifications regulate transcriptional accessibility across the cell cycle.
3
Assess the role and localization of linker histone H1H1.
Establish that histone H1H1 is external to the core octamer and facilitates 30 nm30\text{ nm} fiber compaction without constituting the core itself.
Only H2AH2A, H2BH2B, H3H3, and H4H4 constitute the interior octameric core.

Anahtar Kavram

Eukaryotic Chromatin Architecture and Nucleosome Organization
Tahmini Süre:1m 15s
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Konular

Cell Biology, Genetics, and Evolution

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