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62 Cards in this Set
- Front
- Back
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What type of experiments can be done to give evidence for positive inducers of cell cycle transitions?
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Cell fusion experiments.
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When a cell in any stage of interphase is fused with a cell undergoing mitosis, what is seen in the fused cell? What do the chromosomes look like?
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Both nuclei undergoing mitosis (condensed chromosomes), but not neat. Chromosomes have a complex pattern (single, double and de-condensed).
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What can we infer from this?
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That the interphase cells are driven by a positive factor present in the mitotic cell, causing premature initiation of mitosis.
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When a G1 cell is fused with an S cell, what is observed? What do the G1 chromosomes look like?
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Both nuclei enter the S phase, so positive factors cause the G1 cell to move into S. Long, single and thin.
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When a cell in S phase is fused with a cell in G2 phase, what is observed?
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The nuclei stay in their respective states, no change in the stage of the cell cycle is observed; there is a delay in mitosis in G2 until the S phase nucleus is ready.
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What do the chromosomes look like in a fusion experiment with a mitotic cell and a G2 cell?
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Abnormally long, double filament formation.
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Why do the chromosomes have this strange form?
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Premature chromosome condensation.
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What are two common model organism for the genetics of the cell cycle?
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Fission yeast
Budding yeast |
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What is the difference between the fission yeast and budding yeast cell cycles?
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Fission: Distinctive G1, S, G2 and M phases.
Budding: S transitions into M phase, no G2 phase. |
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Are the yeast chromosomes haploid or diploid?
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Haploid
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What type of mutant of the yeast is used in cell cycle experiments? What is the special about them?
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cdc mutants, which only progress through the cell cycle at low temperatures and are arrested at high temperatures.
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What are the three stages a budding yeast can be arrested at?
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No bud
Small bud Large bud |
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At what temperature do budding yeast cells arrest?
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36 degrees celsius.
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When the temperature threshold is reached, do all the cells arrest with the same morhpology?
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Yes (since they are all arrested at a particular point of the cell cycle)
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Are later events of the cell cycle dependent on earlier events?
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Yes.
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How do fission yeast grow and divide?
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Grow from the tips then divide down the middle.
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What are the mutants that produce small fission yeast called? Why are the yeast small?
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Wee1 mutants, since cytokinesis occurs too quickly.
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What are the mutants that produce long, threadlike yeast called? Why are the yeast small?
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Cdc25 mutants, since cytokinesis does not occur.
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What is a cyclin and how do its levels vary throughout the cell cycle?
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Proteins that control the progression of cells through the cell cycle by activating cyclin-dependent kinase; levels fall and rise depending on the stage of cell cycle (all fall during cytokinesis).
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How do cells move into mitosis?
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Synthesis and phosphorylation of cyclins.
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How do cells move out of mitosis?
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Cells need to dephosphorylate and degrade cyclins (ubiquitination)
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What is used to degrade the cyclin?
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Ubiquitin and proteasome.
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Revise ubiquitination and protein degradation from TDC!
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How are sister chromatids held together?
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Using ring-forming cohesin.
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How can the ring be cleaved? When is it cleaved?
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Using a protease called separin. From the transition of metaphase to anaphase (when the chromosomes split)
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On top of cyclin, what other enzyme is ubiquitinated and degraded during late metaphase? What is its action?
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Secretin, which inhibits the production of separin.
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What are the two components of microtubules?
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Alpha-tubulin
Beta-tubulin |
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What is the name given when the microtubule is shrinking?
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Catastrophe
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What is the name given when the microtubule is growing?
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Rescue
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What is the name of the growing and shrinking nature of the microtubules?
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Dynamic instability.
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How can the top of the growing microtubule be stopped from undergoing catastrophe?
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With the GTP cap
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Is GTP bound tubulin more or less stable than GTP not bound?
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Less stable
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What is the mitotic spindle made of?
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Microtubules
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Where does the mitotic spindle attach?
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To the kinetochore on the chromosomes.
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From where do the microtubules radiate?
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The centrosome.
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What tool can be used to visualise the mitotic spindle?
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Green fluorescent protein (GFP)
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How does cytokinesis occur?
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An actin/myosin ring forms, which then contracts and cleaves the cell.
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How does the cell 'know' when the chromosomes are aligned and ready to split?
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Unaligned chromosomes signal to the cell to delay splitting until they are lined up.
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Where are the various signals and checkpoints which can stop the cell cycle?
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DNA damage at the start S phase
DNA damage during G2 Spindle damage at the start of Mitosis |
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What type of mutant removes the signals and checkpoint ability so the cell cycle cannot be stopped? What phenomenon do these often show?
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Hartwell rad mutants (this is the test to see the role of the proteins). Aneuploidy.
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What is aneuploidy?
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When cells have an incorrect number of chromosomes?
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What is the name of the point which decides whether or not the cell will enter the cell cycle or not?
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The restriction point
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What is an example of biochemistry proving fruitful in cell cycle research?
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mpf discovering the the rapid cell cycles of embryonic cells.
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Do cyclin dependent kinsases or cyclin push the cell through the cell cycle?
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CDKs
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What is the checkpoint for the transition from metaphase to anaphase?
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Spindle (if damaged, cell cycle stops)
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Can microtubules forming the spindle meet in the middle and overlap?
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Yes.
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What is the difference between the kinetochore and the centromere?
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There are two kinetochores, one on each chromosome. There is one centromere, where the chromosomes meet and are linked.
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What makes up one kinetochore?
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Inner and outer kinetochores.
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Where on the kinetochore do the microtubules bind?
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The outer kinetochore
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Where on the kinetochore does the chromosome bind?
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The inner kinetochore
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Where is the centromere in respect to the kinetochore?
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In between.
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How can chromosome loss be measured?
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A plasmid can be bound to a chromosome, if it is maintained, colonies are a solid red colour, and if it is lost, they become white and red.
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Review ANAPATH comparison between apoptosis and necrosis in the AnaPath syllabus.
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What are the 4 types of nematode mutants?
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Egl: Egg laying
Lin: Lineage Nuc: Nuclease Abnormal Ced: Cell Death Abnormal |
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Where does the majority of cell death take place?
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Nervous system
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Revise intrinsic an extrinsic pathways for apoptosis in Anapath notes. Also caspase action.
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What cellular components are digested during apoptosis?
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DNA, cytoskeleton, proteins, nucleus
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What amino acid is present in the caspase active site?
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Cysteine
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What are survival factors?
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Signalling molecules that prevent too much cell death from occurring.
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What is an example of survival factor action in the nervous system?
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Multiple nerve cells forming connections with single target cells, and then some dying so only one neurone connects to the cell.
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What determines if a survival factor binds to a cell and keeps it alive?
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A particular molecule being secreted by the cell.
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What is an example of a survival factor, and what is its action?
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Bcl-2 (B Cell Lymphoma 2), keeps cytochrome C inside mitochondria by closing channels in the outer membrane.
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