Cell Bio 406 Lecture 6

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  1. What contains most of cell's DNA?
  2. What surrounds the nucleus?
    double membrane known as the nuclear envelope.
  3. What is within the nucleus?
    unbound subcompartments
  4. What are nuclear pores for?
    protein import and RNA export.
  5. What do nuclei vary in accordance with?
    cell type and organism.
  6. Where are chromosomes?
    in distinct territories within the nucleus.
  7. What occurs in the nucleolus?
    rRNA synthesis and ribosomal subunits are assembled.
  8. What does the nucleolus contain?
    DNA encoding rRNAs.
  9. What do nuclear speckles do?
    stores splicing factors
  10. What are Cajal bodies?
    may assemble ribonucleoproteins required for splicing.
  11. How many Cajal bodies in the nucleus?
    one or a few
  12. What are PML bodies?
    promylocytic leukemia bodies.- contain chromatin remodeling enzymes and transcription factors.
  13. What may organize all of the nuclear processes?
    nuclear matrix
  14. What does outer nuclear membrane continue to?
    ER membranes
  15. What is the nuclear lumen continuous with?
    ER lumen
  16. What is an NPC?
    channel for transport of molecules between nucleus and cytoplasm.
  17. What does nuclear lamina do?
    provides physical support for nuclear envelope
  18. What is nuclear lamina constructed from?
    lamins- intermediate filament proteins
  19. How does lamina connect to inner membrane?
    lamina-associated integral membrane proteins
  20. How does nuclear lamina organize replication and transcription?
    by connecting to chromatin
  21. What lacks lamina
    yeast and other unicellular eukaryotes
  22. Where is the nuclear lamina located?
    beneath the inner membrane
  23. How do small uncharged molecules transport between cytoplasm and nucleus?
    pass through the membranes of the envelope
  24. What is an NPC
    nuclear pore complex
  25. If too large, how to molecules pass from cytoplasm to nucleus?
    through an NPC with passive or active transport
  26. What is required for nuclear localization?
    sequence information
  27. how do proteins enter and exit the nucleus
    through nuclear pores
  28. Where is information for nuclear import?
    in a small portion of the transported protein
  29. What is NLS?
    nuclear localization signal0=- short stretch of amino acids that targets proteins to the nucleus.
  30. How many steps to nuclear import?
  31. what are the steps of nuclear import?
    • NLS-dependent docking
    • translocation into nucleoplasm (via RAN GTPase)
  32. How is nuclear export mediated?
  33. What is the most common Nuclear export sequence?
    short stretches of amino acids rich in lucine
  34. Nuclear export receptors....
    bind proteins that contain NESs in the nucleus and transports them to the cytoplasm.
  35. What controls the direction of nuclear transport?
    Ran GTPase
  36. What promotes hydrolysis of GTP by Ran?
  37. What promotes exchange of GDP for GTP on Ran?
  38. Where is Ran-GAP located?
  39. Where is Ran-GEF located?
  40. What is exported from the nucleus to the cytoplasm?
    mRNAs, tRNAs, and ribosomal subunits
  41. how is export of RNA mediated?
  42. Is RNA export energy dependent?
  43. How are ribosomal subunits exported?
    assembled in the nucleolus and exported by exportin 1
  44. Where is rRNA made?
  45. What is imported to make ribosomal subunits?
    ribosomal proteins
  46. What is required for ribosomal subunit export?
    Ran/Exportin1 (Crm1) and Nmd3
  47. What is involved in mRNA export?
    NXF1/TAP is the mRNP receptor
  48. What is mRNP?
    mature mRNA and binding proteins
  49. Define chromosome.
    single strand of DNA containing genes and their regulator proteins
  50. Define chromatin
    state of nuclear DNA and its associated proteins during interphase
  51. Define chromatid
    copy of a duplicated chromosome
  52. how is chromatin divided?
    • heterochromatin- densely packed
    • euchromatin- less packed. often undergoing transcription
  53. when can chormosomes be seen
    only during mitosis
  54. What is a nucleosome?
    subunit of chromatin shaped like a cylinder with DNA organized into 1 2/3 turns around the surface
  55. What does a nucleosome contain
    2 copies of each core histone H2A, H2B, H3, and H4.
  56. Core DNA is..
    146 bp found on core particles produced by prolonged digestion with MNase.
  57. What is linker DNA?
    8-114bp that is susceptible to early cleavage
  58. How are histones modified?
    methylation, acetylation, phosphorylation
  59. What is histone code?
    combination of specific histone modifications that define the function of local regions of chromatin
  60. What does SWI-SNF do?
    remodels chromatin to allow for binding of proteins to promoter regions.
  61. What recruits SWI-SNF?
    factors to the DNA
  62. What allows SWI-SNF to carry out functions
    ATPase activity
  63. What is a centromere?
    constricted region of a chromosome that includes the site of attachment to the mitotic or meiotic spindle
  64. How are chromosomes pulled to the poles?
    via microtubules that indirectly attach at the centromeres
  65. How are centromeres identified?
    by a DNA sequence that binds specific proteins that link the chromosome to the cytoskeleton
  66. What allows plasmids to segregate accurately at mitosis?
  67. What mediates binding to microtubules?
    protein complexes formed at CEN elements.
  68. What are CEN elements?
    CDE-I, II, III short conserved sequences
  69. What is a telomere?
    region of repetitive DNA at the end of the chromatid
  70. What does a telomere do?
    protects the chromosomes from degradation at gene ends
  71. What happens to telomeres?
    get shorter with each cell division
  72. Where is telomerase expressed?
    in actively dividing cells, not quiescent cells.
  73. What does loss of telomeres result in?
  74. How can escape for senescence occur?
    if telomerase is reactivated
  75. What causes telomeres to shorten in each cell division?
    mutation in telomerase
  76. What is FISH used for?
    to detect chromosomal abnormalities
  77. What is FISH?
    florescent in situ hybridization- detect different alleles or DNA compositions at the chromosomal level
  78. What is required for FISH?
    labeled probe and a control
  79. What is a polytene chromosome
    chromosomes found at the interphase nuclei of flies
  80. in polytene chromosomes what is DNA rich?
  81. in polytene chromosomes what is DNA poor?
  82. When do polytene chromosomes expand?
    at sites of DNA expression
  83. What is a chromosomal puff?
    region in which chromosome fibers are unwound
  84. What do puffs reflect?
    gene transcription
Card Set:
Cell Bio 406 Lecture 6
2013-08-03 06:40:11
Cellular Biology 406

nuclear structure and transport
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