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15 Cards in this Set
- Front
- Back
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What is the cell cycle? |
The mechanism by which a cell duplicates it's contents and divides in two. |
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What does the cell cycle require? |
1. Replication of DNA and of cellular contents 2. Partitioning of the duplicated material into two "daughter" cells |
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What are the 4 phases of the eukaryotic cell cycle? |
1. M phase: includes mitosis and cytokinesis. ~1hr 2. G1 (Gap 1) phase: interval between M phase and S phase. ~11hrs 3. S phase: DNA replication. ~8hrs 4. G2 (Gap 2) phase: interval between S phase and M phase. ~4hrs |
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What is interphase? |
The period including G1-S-G2 phases. During interphase the cells continues to transcribe it's genes, translate it's proteins, grow and duplicate some of its organelles and grow in mass. |
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How are chromosomes held together? |
By a protein complex called cohesin. Sister chromatic are attached at the centromere. The centromere is the assembly point of the kinetochore |
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What is the order of mitosis? |
1. Prophase 2. Prometaphase 3. Metaphase 4. Anaphase 5. Telophase Then to cytokinesis |
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Prophase |
- chromatin starts to condense - two daughter centrosomes separate and move to opposite poles of cell - spindle poles give rise to interacting sets of microtubules form mitotic spindles |
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Prometaphase |
- chromosomes fully condensed - nuclear envelope breaks down, membrane fragments into small vesicles - microtubules attach to chromosomes via kinetochore, called kinetochore microtubules |
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Metaphase |
- Chromosomes align at the equator of spindle forming the metaphase plate. - kinetochore microtubules from one spindle poles attach to one sister chromatid. Other spindle pole attaches to other sister chromatid. |
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What are the three types of microtubules used during mitosis? |
1. Kinetochore microtubules: attached to condensed chromosomes at centromeres via kinetochores. Play a critical role in seperation. 2. Interpolar microtubules: not attached to chromosomes, overlap each other. Are stabilized by proteins called spindle kinesins 3. Aster microtubules: extend outward from centrosomes to cell periphery and have freely exposed + ends |
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Anaphase |
- paired chromatic synchronously separate forming two daughter chromosomes - daughter chromosomes pulled toward the spindle pole it is attached to |
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How do the three microtubules help pull the chromosomes apart during anaphase? |
1. Kinetochore microtubules disassemble but remain attached to chromosomes, pulling the chromatids to opposite spindle poles. 2. The spindle kinesins of the interpolar microtubules generate a sliding force to push the microtubules apart. 3. The aster microtubules are pulled towards the cell periphery by dynein is anchored to the plasma membrane, this also forces the spindle poles apart |
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Telophase |
- separated chromosomes arrive at the spindle poles - nuclear envelope begins to reassemble - chromosomes start to decondense - contractile ring composed largely of actin microfilaments starts to form at the equator between the two spindle poles |
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Cytokinesis |
1. Cytoplasm is divided in two by the contraction ring. Closure of the cleavage furrow is aided by non-muscle myosin II 2. Equal distribution of cytosolic components to the daughter cells 3. Chromosomes fully decondense, nuclear envelope is reformed 4. Microtubules emerge from the single centrosome in each daughter cell. |
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What effects can improper cell division have on health? |
Aneuploidy: abnormal amount of chromosomes in a cell Down syndrome: trisomy 21, chromosome 21 has 3 copies. Cancer: uncontrolled cell growth. |
