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Cell Bio- Nucleus


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secondary union of originally separate cells and the precursors are nonfunctional
perinuclear cisterna
space that separates inner and outer nuclear membrane
nuclear lamina
layer made of IF (lamin) that separates the nuclear envelope from regions of peripheral heterochromatin
snRNPs- small nuclear ribonucleoprotein particles
proteins that assist in splicing to produce mRNA
Fibrillar region
nucleolar region made of ribosomal DNA that codes for the production of rRNA that is actively being transcribed
Granular region
nucleolar region made of maturing preribosomal subunit particles
Nucleolar-orgainizing regions
parts of chromosomes 13, 14, 15, 21,and 22 gene loci that encode rRNA and are located in the Nucleolus
highly condensed, transcriptionally inactive chromatin
extended, dispersed transcriptionally active chromatin
constituitive heterochromatin
heterochromatin that is never uncoiled
facultative heterochromatin
packed chromatin that contains coding sequences and may or man not be unfolded
barr body
type of facultative heterochromatin that is never uncoiled
generation time
time of one cell cycle and dependent mainly on the G1
phase of cell cycle of synthesis of proteins and specialized functions of the cell
phase of cell cycle when DNA is duplicated and histones are produced
phase of cell cycle when the cell is prepared for mitosis
phase of cells that have left the cell cycle, called end cells
stem cells
cells of same type that haven't become sufficiently specialized and can undergo mitosis and continue to cycle.
progenitor cells
cells that can proliferate but usually lose capacity for self renewal and become committed to produce a single type of end cell
Cyclin-dependent kinases
proteins that for a complex with cyclins and then phosphorylate other proteins to initiate or block activities crucial to progress through cell cycle
tumor suppressor protein that is a Cdk inhibitor and is absent in many cancers
D-type Cyclins
cyclins needed at the G1 checkpoint to activate Cdk 4 and 6 and allow cells to progress to the S phase
MPF- M phase promoting factor
a cyclin B-Cdc 2 complex with kinase activity that is the command to enter mitosis that accumulates in G2 at the checkpoint
protein structure that links centromere of chromosomes to spindle microtubules during mitosis
enzyme that elongates existing telomere making cells 'immortal'. Only activated in cancer
DNA attached to short arms of chormosomes 13, 14, 15, 21 and 22 bye secondary constriction and contains rRNA genes. These fuse to form the nucleolus after mitosis
active form of cell death initiated by the cell. Programmed elimination of the cell
enzymes which degrade regulatory and structural proteins in nucleus and cytoplasm.
What is they cytosolic side of the nucleus surrounded by?
a thin loose network of IF and ribosomes actively synthesizing transmembrane proteins for the envelope
what provides the structural framework to facilitate and organize the complex events of RNA and DNA synthesis and processing?
nuclear matrix- including the nuclear lamina and steroid receptor binding sites
What is the amount of protein synthesized in a cell related to?
the size of the nucleolus
What is the nucleolus composed of?
Fibrillar regions, fibrillar centers, granular regions and nucleolar matrix
what are the three forms (locations) of heterochromatin?
peripheral, nucleolar associated, and chromatin islands
2 types of heterochromatin
constituitive or faculatative
2 examples of constituitive heterochromatin?
centromeric and satellite DNA
3 phases of interphase
G1, S, G2
What is the maximum number of times an average cell divides
what are the two fates of daughter cells of stem cell division?
remain stem cells and not differentiate more than parent, or become progenitor cells
3 types of stem cells
multipotential, pluripotential, or unipotential
5 environmental regulators of cell division
1)nutrients; 2) conact with neighboring cells 3)contact with ECM 4) hormones 5) growth factors
how do growth factors regulate cell proliferation?
through intracellular signalling cascades which ultimately regulate gene transcription and assemble and activation of the cell cycle control system
What has a constant concentration throughout the cell cycle, and what has variable concentrations?
cyclins go up and down through the cell cycle but Cdk has a constant concentration
What are the two cell cycle checkpoints?
G1 and G2
What are cell cycle checkpoints dependent on?
sufficient cdk-cyclin complexes to overcome inihibitions and proceed
What phosphorylates the Rb gene product?
D-Cdk complexes
Which is the activated form of Rb? what does it do?
unphosphorylated form and it inhibits transition for G1 --> S
What signals excessive damage to genetic material and halts the cell cycle in G1?
sufficient concentration of p53
Which is the most regulated cell cycle phase?
G1. G1 checkpoint very specific
What is MPF inhibited by?
incompletely replicated DNA
what does MPF induce?
chomosomes to condense, nuclear envelope to break, cells to round up, reorganization of cytoskeleton
What signals chromosomes to condense
phosphorylation of histone 1 by MPF
what signals the nuclear envelope to break
phosphorylation of lamin by MPF
what signals the reorganization of the cytoskeleton?
phosphorylation of microtubule associated protein by MPF
What happens at the Metaphase checkpoint?
tag cyclin with Ubiquitin, inactivate MPF
when do chromosomes reach their most compact state?
end of metaphase
what is apoptosis regulated by
coding of caspase genes
Stages of apoptosis
1) cell shrinkage 2) chromatin condensation (pyknosis) 3) formation of cytoplasmic blebs and apoptic bodies 4)phagocytosis by adjacent cells
chromatin condensation that occurs in apoptosis

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