HISTOLOGY-Lecture 2-Nucleus

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lfield5
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64765
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HISTOLOGY-Lecture 2-Nucleus
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2011-02-09 03:28:42
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Lecture 2-Nucleus
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  1. Nucleus (shape)
    • shape
    • -round - usually
    • -spindle to oblong
    • -twisted
    • -lobulated
    • -disc shaped
    • -largest organelle of the cell
  2. Nucleus (structure. location & number)
    • structure
    • -nuclear membrane
    • -chromatin
    • -nucleolus
    • -nucleoplasm

    • location
    • -centrally - usually
    • -peripheral

    • number
    • -one -usually
    • -many -skeletal muscle
    • -non -RBC
  3. Nucleus (function)
    • function
    • -contains nearly all the DNA
    • -RNA synthesis
    • -assembly of RNA subunits
  4. Nuclear Membrane (structure)
    2 unit membrane

    • -outer nuclear membrane
    • -perinuclear cisterna - space between
    • -inner nuclear membrane
  5. Outer Nuclear Membrane
    (Nuclear Membrane - Nucleus)
    • faces the cytoplasm
    • continuous with RER

    • cytoplasmic surface contains:
    • -ribosomes - synthesize outer/inner transmembrane proteins
    • -vimentin - intermediate filaments - meshwork cover - acts as an anchor
  6. Inner Nuclear Membrane
    (Nuclear Membrane - Nucleus)
    faces the nuclear contents

    in close contact with nuclear lamina

    • function: contact sight for
    • -nuclear RNA's
    • -chromosomes
  7. Nuclear Lamina
    (Nuclear Membrane - Nucleus)
    meshwork of intermediate filamens

    located at periphery of nucleoplasm

    • function: organize/support
    • -inner membrane
    • -perinuclear chromatin
  8. Nuclear Pore Complex - function & characteristics
    • function
    • -communication between nucleus & cytoplasm
    • -semipermeable
    • -assists in organizing chromatin

    • characteristics
    • -inner/outer membrane merge together
    • -pore spans the two membranes
    • -pores communicate viw nuclear lamina & pore-connecting fibers
  9. Nuclear Pore Complex - structure
    composed of multiple rings

    • 1. CYTOPLASMIC RING
    • -8 subunits
    • -located: cytoplasmic rim
    • -thick filament attached to ring & extends into cytoplasm

    • 2. THIN RING
    • -fits ino cytoplasmic ring

    • 3. STAR RING
    • -supports thin ring & cytoplasmic ring

    • 4. SPOKE RING COMPLEX (middle ring)
    • -8 subunits
    • -transmembrane proteins
    • -spokes project into perinuclear cictern - acts as anchors - gated channel

    • 5. TRANSPORTER
    • -center of middle ring
    • -coupled to spokes

    • 6. NUCLEOPLASMIC RING
    • -8 subunits
    • -located : nucleoplasm side
    • -assists ins export of RNA

    • 7. NUCLEAR BASKET
    • -suspended from nucleoplasmic ring
    • -protrudes into nucleoplasm
    • -deforms during export

    • 8.DISTAL RING
    • -holds the basket together
  10. Nuclear Pore Complex - transport
    • pore size: 9-11nm
    • -diffusion into/out of if small

    • >11 nm
    • -receptor mediated transport
    • -requires GTP


    RECEPTOR MEDIATED TRANSPORT

    • Exportins
    • -transport proteins
    • -transport macromolecules from nucleus to cytoplasm
    • -GTPRan + export binds to cargo
    • -GDPRan = release of exportin + cargo

    • Importins
    • -transport proteins
    • -transport cargo from cytoplasm to nucleus
    • -GDPRan + importin binds cargo
    • -GTPRan = release of importin + cargo
  11. Chromatin
    uncoiled DNA strands

    • Heterochromatin-
    • -condensed inactive DNA
    • -located mostly on periphery of nucleus
    • -visible with light microscope

    • Euchromatin-
    • -uncondensed active DNA
    • -transcription
    • -not visible with lighy microscope

    • Nucleosome
    • -simplest arrangement of chromatin
  12. Heterochromatin
    • -condensed inactive DNA
    • -located mostly on periphery of nucleus
    • -visible with light microscope
  13. Euchromatin
    • -uncondensed active DNA
    • -transcription
    • -not visible with ligh microscope
  14. Nucleosome - definition & function
    simplest arrangement of chromatin

    • fuction
    • -provides strucutral framework for chromatin
    • -thought to be region of transcription
    • -control mechanism for DNA repair, replication, transcription
  15. Nucleosome - structure
    • protein beads
    • -4 types of HISTONES
    • 1. H1 - holds DNA in coils
    • 2. H2A & H2B
    • 3. H3
    • 4. H4


    • DNA
    • -2 turns around bead
    • -linker DNA links nucleosomes together
  16. Chromosome
    extensively condensed inactive DNA

    • -visible with light microscope
    • -maximum condensation of DNA
    • -apparent only during cell division

    • anatomy:
    • G-bands
    • Arms
    • Telomere
    • Centromere
  17. G-Bands - Chromosome
    • giesma stain of adenin-thymine rich regions
    • unique for each chromosome pair
    • characteristic specific
  18. Arms - Chromosome
    p arm - short arm

    q arm - long arm
  19. Telomere - Chromosome
    function - prevents DNA deterioration

    • cap at end of chromosome
    • nucleotide repeats
  20. Centromere - Chromosome
    • narrow end on chromosome
    • nucleotide repeats
    • where sister chromatids come together
  21. Genome - Chromosome
    specific number of chromosomes for a given species


    • makeup
    • -homologus pairs - double set
    • -autosomes - pairs 1-22 in humans
    • -sex chromosomes
    • 23 pairs
    • XX female Xy male


    • Sex Chromatin - Barr Body
    • -found in females
    • -highly coiled clump of chromatin
    • = inactive X chromosome
    • - found in edge of nuclear membrane
  22. Sex Chromatin - Barr Body (Genome- Chromosome)
    • -found in females
    • -highly coiled clump of chromatin
    • = inactive X chromosome
    • - found in edge of nuclear membrane
  23. Ploidy
    sets of chromosomes

    • Haploid (1N)
    • -1 set chromosomes
    • -gametes

    • Diploid (2N)
    • -2 sets of chromosomes
    • -somatic cells

    • Triploid (3N)
    • -3 sets of chromosomes
  24. Karyotype
    number of chromosomes


    • aneuploidy
    • -abnormal chromosome number
  25. Nucleoplasm
    contents of the nucleus minus the chromatin

    • consists of
    • -ribonucleoprotein particles (RNP)
    • -interchromatin granules (IG)
    • -perichromatin granules (PCG)
    • -nuclear matrix
    • -nucleolus
  26. Ribonucleoprotein Particles (RNP)
    compound that combines RNA and protein

    • composed of-
    • Heterogeneous nuclear ribonucleoproteins (hnRNP)
    • Small Nuclear Ribonucleoprotein Particle


    component of Nucleoplasm
  27. Heterogeneous Nuclear Ribonucleoproteins (hnRNP)
    • function:
    • -signal pre-mRNA not finished
    • -target introns of degradation

    component of Nucleoplasm
  28. Small Nuclear Ribonucleoprotein Particle (snRNP)
    • function:
    • -splicing hnRNP
    • -cleaving hnRNP
    • -transporting hnRNP

    • located:
    • -nucleus - most
    • -nucleoli - some

    • types:
    • -U1, U2, U4, U5, U6
    • -U11 etc rare

    component of Nucleoplasm
  29. Interchromatin Granules (IG)
    • composed of clusters
    • -Ribonucleoprotein (RNP)
    • -enzymes
    • *ATPase
    • *GTPase
    • *beta-glycerophosphatase
    • *NAD-pyrophosphatase

    • located:
    • -in clusters throughout and among chromatin

    connected to each by fibrils - possibly

    FUNCTION UNKNOWN

    component of Nucleoplasm
  30. Perichromatin Granules (PCG)
    • located:
    • -on the margins of heterochromatin

    • surrounded by:
    • -halo of less dense material

    • composed of:
    • -densely fibrils of 4.7S RNA
    • -two peptides
    • *heterogeneous nuclear ribonucleoproteins (hnRNP)


    component of Nucleoplasm
  31. Nuclear Matrix
    • composed of:
    • -10% protein
    • -30% RNA
    • -1-3% DNA
    • - 2-5% nuclear phosphate

    • function:
    • -DNA replication sites
    • -rRNA/mRNA transcription/processing
    • -steroid receptor binding
    • -heat shock proteins
    • -carcinogen binding
    • -DNA viruses
    • -viral proteins

    • structure:
    • -residual nucleoli
    • -residual RNP networks
    • -fibrillar elements
    • -nuclear pore-nuclear laminar complex
    • *interwoven meshwork of intermediate filaments
    • *located on periphery of nucleoplasm
    • * function- organize and support
    • -lipid bilayer membrane
    • -perinuclear chromatin



    component of Nucleoplasm
  32. Nucleolus (describe)
    • -dense
    • -nonmembranous
    • -visible only during interphase
    • -dark staining
    • -active = 25% of nuclear volume
    • -generally 2-3 per cell



    component of Nucleoplasm
  33. Nucleolus (composition)
    • DNA
    • -only small amounts
    • -inactive

    rRNA rich

    Protein


    component of Nucleoplasm
  34. Nucleolus (regions)
    • nucleolus-associated chromatin
    • -densely staining material
    • -chromatin being transcribed in rRNA

    • regions:
    • 1. pale-staining fibrillar center - inactive DNA
    • 2. pars fibrosa - nucleolar RNA transcription
    • 3. pars granulosa - ribosomal subunit assembly
    • 4. nucleolar matrix - fiber network - organization

    • nuclear organizer region (NOR)
    • -active after cell division
    • -located in pale staining area
    • holds:
    • *the tips of chromosomes - 13, 14, 15, 22 (in humans)
    • *genes loci that encode rRNA


    component of Nucleoplasm
  35. Nuclear Organizer Region (NOR)
    • -active after cell division
    • -located in pale staining areaholds:
    • *the tips of chromosomes - 13, 14, 15, 22 (in humans)
    • *genes loci that encode rRNA


    component of Nucleoplasm

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