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Nuclear Structure

COMPONENTS OF NUCLEUS • Nucleolus • Chromatin • Nucleoplasm • Nuclear envelope: compartmentalizes nucleus and its contents
NUCLEAR ENVELOPE • Outer and inner nuclear membranes (perinuclear space between them) • Porous with nuclear pore complexes • Continuous with endoplasmic reticulum • Ribosomes on the surface • Nuclear lamina: comprises lamins, provides structural support to nucleus and organizes heterochromatin
NUCLEOPLASM • Medium within the nucleus (mostly water) • Suspends nucleolus and chromatin
NUCLEOLUS • Lacks a membrane • Functions in rRNA synthesis and assembly of ribosomal subunit precursors
CHROMATIN • Comprises DNA and associated proteins • Functions in DNA compaction and protection • Regulates and controls transcription • Heterochromatin: gene-poor, rich in histone modifications, densely packed, tethered to nuclear lamina at periphery of nucleus • Euchromatin (the rest): transcriptionally active and loosely packed; distributed throughout the nucleus
CLINICAL CORRELATION
Laminopathies
  • Mutations in nuclear lamins; diverse group of disorders ranging from myopathies to progeria