Gre Bio Chp 5 Cell Cycle

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Phases of the cell cycle

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G1 (growth), G0 (resting), S (DNA synthesis), G2 (growth), mitosis

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Centrioles

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copy during the S phase and move to opposite poles of the cell. Form the foundation for centrosomes

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Prophase

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First phase of mitosis. Chromatin show up as well defined chromosomes. Mitotic spindle begins to form and elongate from centrosome region

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Prometaphase

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Second phase of mitosis. Nuclear membrane dissolves. Spindle microtubules attach to chromosomes. Microtubules that attach are called kinetochore microtubles. Those that do not attach are called nonkinetochore or polar microtubules

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Metaphase

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Third phase of mitosis. Kinetochore microtubules push from opposite poles to align chromosomes in the middle of the cell in an area called the metaphase plate.

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Anaphase

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The fourth phase of mitosis. Chromatids separate as kinetochore microtubules shorten rapidly. Polar microtubules lengthen, pushing poles of cells farther apart.

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Telophase

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Fifth phase of mitosis. Separated chromatids group at opposite ends of the cell near the centrosome region. Nuclear envelope reforms. Mitosis ends.

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Cytokinesis

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Contractile ring of actin shortens center of cell, creates cleavage.

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Cell cleavage in plants (M Phase)

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A new cell wall is created along the metaphase plate. Small membrane bound vesicles filled with cell wall precursors merge along the straight line guided by polar microtubules.

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Cell Plate

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The merged vesicle structure that forms the new cell wall during cleavage in plants.

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Checkpoints

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Points in the cell cycle that determine whether the cell will proceed to the next stage

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cyclin-dependent protein kinases (Cdk)

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Proteins that regulae passage through the cell cycle. Once activated, Cdks activate other proteins to initiate the next step in the cell cycle.

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cyclins

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Proteins that bind to Cdks. At every step in the cell cycle a different cyclin binds to a different Cdk.

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Proto-oncogenes

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Normal genes involved in the control of cell growth and division.

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Oncogenes

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Genes that have mutated so that they no longer maintain control over a particular aspect of growth or cell division.

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Genes associated with cell division

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Growth factors, growth-factor receptors, intracellular sign-inducing proteins, and nuclear transcription factors

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Growth Factors

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Act on cell surface receptors that bind in a specific manner, causing those cells to initiate growth and cell division. Different growth factors are released by different kinds of cells. Increasing growth factor alone is not sufficient for inducing cancer

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Density-dependent inhibition of cell division

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The phenomenon where normal cells suppress their growth when near other cells.

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Growth Factor Receptors

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Membrane spanning proteins that have an area to bind with growth factors. They transmit a signal via second messengers

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Intracellular Signal Transducing Proteins

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Second messenger proteins that carry signals from the cell surface to the nucleus. Relay signals that will turn on/off certain genes (Ras and Src)

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Nuclear Transcription Factors (NTFs)

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Proteins that facilitate the activation of particular genes (fos and myc). Abnormally activated transcription factors can increase production of cyclins and other mitosis inducing proteins.

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Apoptosis

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The process of removing error filled DNA or causing precancerous cells to kill themselves

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p53 and pRB

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Proteins that act as tumor suppressors. Many human tumor cells lack these proteins.