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mitosis
biol 1210
| Question | Answer |
|---|---|
| requirements for cell division | 2 daughter cells must receive full complement of genetic material in parent cell & parent cell must be large enough to divide in 2 and contribute sufficient cytoplasmic components to daughter cells |
| how do prokaryotic & eukaryotic cells divide? | prok - binary fission, euk - mitosis & cytokinesis |
| 3 events for a cell to divide | 1. copying the DNA, 2. separating copies of DNA, 3. dividing cytoplasm to create 2 complete cells |
| difference btwn genetic material of prok & euk cells | prok - circular chromosome, single DNA strand, no nucleus (nucleoid region). Euk - linear chromosomes, double DNA strands, nucleus |
| events of binary fission | 1. DNA replication, 2. size increase, 3. divides into 2 daughter cells - each receives 1 copy of parent's DNA |
| list proteins involved in mitosis | cohesins, condensins, nuclear lamins, kinetochore proteins, microtubules |
| cohesins | proteins that form rings that hold sister chromatids together |
| condensins | ring-shaped proteins that condense DNA |
| nuclear lamins | intermediate filaments that form an interface btwn chromosome & inside of the nuclear envelope (which disintegrates for mitosis) |
| kinetochore proteins | sites where microtubules connect to chromosomes |
| microtubules (during mitosis) | move chromosomes to the poles of the cell |
| spindle apparatus structure & function | made of microtubules formed from microtubule-organizing centres (MTOCs). Produces mechanical forces that move replicated chromosomes during metaphase & pull chromatids apart in anaphase |
| MTOCs in animals & plants | in animals cells: centrosomes each w pair of centrioles, plant cells: NEDD1 complexes |
| describe spindle apparatus poles | MTOCs define the poles, w center neg charged & positive ends that grow outwards from each pole. Polar MT extend towards chromosome & overlap; Astral MT anchors MTOCs; Kinetochore MT attach to kinetochores at centromeres |
| stages of cell cycle | M phase: time of cell division & interphase: time between two successive M phases |
| interphase | cells spend most of their time in interphase when chromosomes r uncoiled & cells are growing & preparing for division or fulfilling their functions |
| describe the 3 stages of interphase | G1 - cell growth & protein content increase, many regulatory proteins activated, S - DNA replication/synthesis, G2 - cell growth & preparing for M phase |
| parts of M phase | 1. mitosis - division of replicated chromosomes, 2. cytokinesis - division of cytoplasm |
| events of prophase | MTOCs migrate from center to poles of cell, spindle apparatus begins to form, chromosomes condense, nuclear lamins set up |
| events of prometaphase (or part of prophase) | nuclear envelope breaks down, spindle apparatus contacts chromosomes at kinetochores |
| events of metaphase | chromosomes align in the middle of the cell (metaphase plate) w MTOCs at poles of cell |
| events of anaphase | microtubules start to depolarize in kinetochores & pull sister chromatids apart |
| events of telophase | chromosomes disconnect from spindle apparatus, nuclear envelope reforms, chromosomes de-condense (reverse of prophase) |
| describe 2 forces that pull the chromatids apart | microtubules are disassembled at kinetochore during anaphase - split by tight kinetochore ring that depolarizes the microtubule & frays the end of the microtubule towards the poles + polar microtubules at ends of cells offer additional force |
| when does cytokinesis occur? | as mitosis ends |
| cytokinesis in animal cells | ring of actin filaments (contractile ring) forms and contracts, pinching cytoplasm of cell & forming cleavage furrow that divides the cell into two |
| cytokinesis in plant cells | vesicles from golgi apparatus bring membrane & cell wall components to middle of cell, forming cell plate - once it is large enough, it fuses w parent cell wall at perimeter of cell & divides cell into two |
| cell division in bacteria, dinoflagellates & diatoms/yeasts | bacteria: binary fission, dinoflagellates: nuclear envelope stays intact, divides, & microtubules go straight the envelope, diatoms/yeasts: nuclear envelope stays intact, divides, & spindle form in nuclear envelopes |
| what varies cell cycle length? | length of the G1 phase - rapidly dividing cells essentially eliminate G1 phase, nondividing cells are permanently stuck in G1 phase (G0 state). Division rate may change in response to environment |
| how many cell cycle checkpoints are there? | 4: one in G1 & G2 and two in M-phase |
| G1 checkpoint | pass if: cell size is adequate, nutrients are sufficient, social signals are present, & DNA is undamaged. Mature cells do not pass (enter G0 state) |
| G2 checkpoint | pass if: chromosomes have replicated successfully, DNA is undamaged, activated mitotic factor (MPF) is present |
| M-phase checkpoints | pass if: 1. chromosomes have attached to spindle apparatus, & 2. chromosomes have properly segregated and MPF is absent |
| how do tumours form? | when cells start dividing rapidly without control |
| 2 types of defects of cancerous cells | 1. defects that activate proteins required for cell growth when they shouldn't be active, & 2. defects that prevent tumour suppressor genes from shutting down the cell cycle |
| 2 types of tumours | 1. benign: noncancerous & noninvasive 2. malignant: cancerous & invasive, can spread throughout body via blood or lymph & initiate secondary tumours (metastasis) |
| cell cycles of differentiated cells (ex. nerve cells) v. undifferentiated | differentiated cells are unlikely to be dividing at all and exist in a G0 state to conduct their functions for the organism. Undifferentiated cells are likely dividing rapidly to grow and mature/form tissues quickly. |
| why are cell cycle checkpoints important? | checkpoints regulate the growth & division of the cells of an organism, preventing most defective/infected cells from continuing onto division. If control was lost, cells would divide uncontrollably and likely kill the organism before it could mature |
| what are kinetochores, and how do kinetochore microtubules differ in function from non-kinetochore microtubules? | the sites for connection of the spindle apparatus to the sister chromatids made of fibres + ring that form around the duplicated chromosomes' centromere. Non-kinetochore microtubules anchor the MTOCs & provide force for pulling sister chromatids apart |
| what happens to chromosome # in cells undergoing mitosis + cytokinesis? What happens if mitosis but no cytokinesis? | chromosome # is distributed equally among daughter cells & is same as the parent cells. Without cytokinesis, mitosis would result in a large multinucleated cell with doubling chromosome # |
| why is it hypothesized binary fission gave rise to mitosis? | some of the proteins used in bacterial binary fission are used in euk cell division & prok precede eukaryotes by billions of years. Unicellular euk. replicate by process similar to binary fission in which the nuclear envelope stays intact |
Created by:
AntBanana
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