Cell Bio- Nucleus
Terms
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- syncytium
- 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
- heterochromatin
- highly condensed, transcriptionally inactive chromatin
- euchromatin
- 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
- G1
- phase of cell cycle of synthesis of proteins and specialized functions of the cell
- S
- phase of cell cycle when DNA is duplicated and histones are produced
- G2
- phase of cell cycle when the cell is prepared for mitosis
- G0
- 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
- p53
- 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
- kinetochore
- protein structure that links centromere of chromosomes to spindle microtubules during mitosis
- telomerase
- enzyme that elongates existing telomere making cells 'immortal'. Only activated in cancer
- satellites
- 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
- apoptosis
- active form of cell death initiated by the cell. Programmed elimination of the cell
- caspases
- 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
- 50-60
- 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
- pyknosis
- chromatin condensation that occurs in apoptosis