cell biology exam 3

cell biology exam 3 - The Cell Cycle and...

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The Cell Cycle and Multicellularity -The cell cycle- aka the cell division cycle- the series of processes and events that allow 1cell---2 cells Very Important because… -provides raw material for development of multicellular organisms -needed to replace cells that die due to old age, injury, disease -Abnormal regulation of cell division results in cancer -Standard cell cycle: the cell division cycle of a typical somatic (non sex) cycle *Cell cycle has G1, S, G2, and M phases --G1= Gap1 phase- Cell grows larger --S= Synthesis phase- DNA is replicated --G2= Gap 2 Phase- More cell growth --M= Mitosis- Cell divides For Standard Cell Cycle G1~11 S~1 ~24 Hours G2~11 M~1 -Standard cell cycle can be considered as having 2 general components *G1 S G2------------purpose for cell division (G1 S G2 = interphase) M-------Cell actually divides Events of Interphase Question: What has to happen to prep cell for division? -DNA has to be copied PRECISELY -Centrosomes has to be copied PRECISELY *other components don’t have to be precisely replicated --PM, Cytoplasm, and single copy organelles (ie. RER, Golgi, nuclear envelope) -Increase in size (or volume in case of cyctoplasm) -Multicopy organelles (ex: mitrocondrial)- Increase in number during interphase -DNA and centrosomes replicated in S phase -Other stuff increase in size/abundance throughout interphase Events of M Phase -4 Subphases of M-phase- prophase, metaphase, anaphase, telophase 1. Prophase- nuclear envelope, RER, and Golgi “breakdown”
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-disasseble into thousands of small vesicles -the vesicles are then distributed more/less randomly throughout cell, ensuring that each daughter cell will eventually get roughly = amounts of vesicles -DNA condenses- goes to tightest possible compaction state, this is needed for rapid and accurate distribution later in M-phase -Mitotic Spindle Forms 2. Metaphase: All events begin in prophase are completed and sister chromatids are lined up in middle of spindle (in metaphase plate) *Although there does not appear to be much happening in metaphase, it is a key decision point for cell, it judges whether or not chromatids are ready to be separated 3. Anaphase: Chromatid separation begins, cytokinesis (pinching in ½ of 2 daughter cells begins) 4. Telophase: Cytokinesis is completed, events of prophase are reversed- organelles reassemble, DNA decodes, etc. . -Decrease kinase turns on! *phosphorylation occurs---causes many events -Nuclear Envelope Breakdown: *Results from at least 3 processes -the nuclear lamins are phosphorylated -results in disassembly of individual lamin -filaments, & as a result, of the lamina as a whole -Lamin Disassembly: makes nuclear envelope weak *Microtubules extend from centromeres, get bound by dynein? on nuclear envelope, dynein moves toward minus end on Microtubules, bringing parts of nuclear envelope and thereby leaving holes in nuclear envelope
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1. Prophase Nuclear Envelope Breakdown -Cop1 Coatamer complex is recruited to Nuclear Envelope by binding to nup153 -Following recruitment, Cop1 coatamer complex drives budding and vesiculation of nuclear
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cell biology exam 3 - The Cell Cycle and...

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