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17 Cards in this Set
- Front
- Back
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T/F: phosphorylation of condensins by m-cdk triggers chromosome condensation.
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True.
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What is the f(x) of
a. actin b. microtubules in mitosis? |
a. Actin (& myosin) form the contractile ring
b. Microtubules form the mitotic spindle |
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When does centriole replication occurr?
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It occurrs in S-Phase.
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What are the steps in the centrosome cycle?
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1. Each centrosome has a pair of centrioles. During S-phase, they start to form at a right angle to the mother. The pairs remain close until the beginning of M Phase.
2. In S/G2, the centriole pairs and the centrosome matrix are a single complex. 3. In early M Phase, the two separate and nucleates its own aster. 4. By late prophase, MT's interacting between 2 asters elongate and form a bipolar spindle. 5. At prometaphase, the nuclear envelope breaks down, and MT's are free to interact with the chromosomes. |
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What occurrs in:
A) Early Prophase B) Late Prophase |
A) Early Prophase: chromosomes condense
B) Late Prophase: MT's have assembled and chromosomes move apart |
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Prometaphase?
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nuclear envelope breaks down, and astral MT's interact with kinetochore on chromosomes (beginning of kinetochore MT formation)
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Metaphase
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chromosomes align along metaphase plate; bipolar spindle is obvious; metaphase plate is equidistant between the two poles
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Early Anaphase/Anaphase A
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cohesins degrade, separating sister chromatids; daughter chromosomes moved towards poles; sister chromatids do not separate until BOTH kinetochores are bound to all MT's (all others will wait until last chromosome is bound)
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Late Anaphase/Anaphase B
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spindle poles move farther apart, enhancing separation of chromosomes
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Telophase
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daughter nuclei have formed
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A) Astral MT
B) Kinetochore MT C) Overlap MT |
A) Astral: radiate all directions; contributes to pole separation; dyenein is attached to cell cortex and astral MT
B) Kinetochore: connect to spindle C) Overlap: interlock @ equator and add symmetrical shape to spindle; kinesin is bound and moves the overlap MT past each other |
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How do kinetochore MT form?
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1. during prometaphase, the sister chromatid kinetochores bind lateraly to the astral MT
2. the chromosomes slide towards the spindle pole 3. kinetochore MT forms when the chromosomes switch from a lateral attachment to a end-on unipolar attachment 4. second MT binds to other free kinetochore, forming a bipolar attachment |
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Cytokinesis
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1. division of cytoplasm
2. starts in anaphase, ends in telophase 3. starts w/ formation of cleavage furrow (formed by contractile ring, which is activated by calcium) |
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In meiosis, when does genetic recombination occurr?
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prophase I in the bivalent; chiasmata are connections formed between the two chromosomes; crossing over is crucial for the segregation of the two duplicated homologs to daughter nuclei
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Metaphase I
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bivalents (homologous chromosomes) line up on the plate; centrioles are found at opposite poles
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What is the end result of meiosis II?
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four haploid cells, each with 23 chromosomes/23 chromatids
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List the 5 stages of the synaptonemal complex in meoitic prophase I.
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1. Leptotene: early prophase; paired homologs condense
2. Zygotene: synaptonemal (synaptic) complex forms b/w sister chromatids 3. Pachytene: synapsis is complete; crossing over occurs; bivalents present 4. Diplotene: bivalent structure disapears; separation 5. Diakinesis: homologous chromosomes condense and shorten; nuclear envelope breaks down |
