Nucleus (shape)
shape-round - usually-spindle to oblong-twisted-lobulated-disc shaped-largest organelle of the cell
Nucleus (structure. location & number)
structure-nuclear membrane-chromatin-nucleolus-nucleoplasm
location-centrally - usually-peripheral
number-one -usually-many -skeletal muscle-non -RBC
Nucleus (function)
function-contains nearly all the DNA-RNA synthesis-assembly of RNA subunits
Nuclear Membrane (structure)
2 unit membrane
-outer nuclear membrane-perinuclear cisterna - space between-inner nuclear membrane
Outer Nuclear Membrane
(Nuclear Membrane - Nucleus)
faces the cytoplasmcontinuous with RER
cytoplasmic surface contains:-ribosomes - synthesize outer/inner transmembrane proteins-vimentin - intermediate filaments - meshwork cover - acts as an anchor
Inner Nuclear Membrane
(Nuclear Membrane - Nucleus)
faces the nuclear contents
in close contact with nuclear lamina
function: contact sight for-nuclear RNA's-chromosomes
Nuclear Lamina
(Nuclear Membrane - Nucleus)
meshwork of intermediate filamens
located at periphery of nucleoplasm
function: organize/support-inner membrane-perinuclear chromatin
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
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
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
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
Heterochromatin
-condensed inactive DNA-located mostly on periphery of nucleus-visible with light microscope
Euchromatin
-uncondensed active DNA-transcription-not visible with ligh microscope
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
Nucleosome - structure
protein beads-4 types of HISTONES1. H1 - holds DNA in coils2. H2A & H2B3. H34. H4
DNA-2 turns around bead-linker DNA links nucleosomes together
Chromosome
extensively condensed inactive DNA
-visible with light microscope-maximum condensation of DNA-apparent only during cell division
anatomy:G-bandsArmsTelomereCentromere
G-Bands - Chromosome
giesma stain of adenin-thymine rich regionsunique for each chromosome paircharacteristic specific
Arms - Chromosome
p arm - short arm
q arm - long arm
Telomere - Chromosome
function - prevents DNA deterioration
cap at end of chromosomenucleotide repeats
Centromere - Chromosome
narrow end on chromosomenucleotide repeatswhere sister chromatids come together
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
Sex Chromatin - Barr Body (Genome- Chromosome)
-found in females-highly coiled clump of chromatin= inactive X chromosome- found in edge of nuclear membrane
Ploidy
sets of chromosomes
Haploid (1N)-1 set chromosomes-gametes
Diploid (2N) -2 sets of chromosomes-somatic cells
Triploid (3N)-3 sets of chromosomes
Karyotype
number of chromosomes
aneuploidy-abnormal chromosome number
Nucleoplasm
contents of the nucleus minus the chromatin
consists of-ribonucleoprotein particles (RNP)-interchromatin granules (IG)-perichromatin granules (PCG)-nuclear matrix-nucleolus
Ribonucleoprotein Particles (RNP)
compound that combines RNA and protein
composed of-Heterogeneous nuclear ribonucleoproteins (hnRNP)Small Nuclear Ribonucleoprotein Particle
component of Nucleoplasm
Heterogeneous Nuclear Ribonucleoproteins (hnRNP)
function:-signal pre-mRNA not finished -target introns of degradation
component of Nucleoplasm
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
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
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
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
Nucleolus (describe)
-dense-nonmembranous-visible only during interphase-dark staining-active = 25% of nuclear volume-generally 2-3 per cell
component of Nucleoplasm
Nucleolus (composition)
DNA-only small amounts-inactive
rRNA rich
Protein
component of Nucleoplasm
Nucleolus (regions)
nucleolus-associated chromatin-densely staining material-chromatin being transcribed in rRNA
regions:1. pale-staining fibrillar center - inactive DNA2. pars fibrosa - nucleolar RNA transcription3. pars granulosa - ribosomal subunit assembly4. nucleolar matrix - fiber network - organization
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
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