Term
| Why do cells need to divide? |
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Definition
-growth
-wound repair
-reproduction |
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Term
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Definition
-everyday functions of cells
-cell metabolically active
-duplicates organelles and cytosolic components
-starts replicating centrosomes |
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Term
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Definition
| DNA is copied/synthesized |
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Term
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Definition
-cell is waiting to divide
-cell growth continues
-enzymes and other proteins are synthesized and replication of centrosomes is completed |
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Term
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Definition
-division of DNA
-mitosis (prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis) |
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Term
| During the _____ phase, the centrosome is duplicated |
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Definition
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Term
| T/F: Neuron/muscle cells don't divide |
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Definition
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Term
| The _____ phase of the cell cycle is like a "permanent" G1 phase in which the cell never again passes the G1 checkpoint |
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Definition
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Term
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Definition
| a structure composed of a DNA molecule and associated proteins |
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Term
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Definition
| the material that makes up eukaryotic chromosomes; consists of a DNA molecule complexed with histone proteins |
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Term
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Definition
| one strand of a replicated chromosome, with its associated proteins |
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Term
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Definition
| the two strands of a replicated chromosome; when chromosomes are replicated, they consist of two sister chromatids; the genetic material in sister chromatids is identical; when sister chromatids separate during mitosis, they become independent chromosomes |
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Term
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Definition
| the structure that joins sister chromatids |
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Term
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Definition
| the structures on sister chromatids where microtubules attach |
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Term
| Microtubule-organizing center |
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Definition
| any structure that organizes microtubules |
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Term
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Definition
| the microtubule-organizing center in animals and some plants |
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Term
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Definition
| cylindrical structures that comprise microtubules, located inside animal centrosomes |
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Term
| A fruit fly cell in G1 of the cell cycle contains 8 chromosomes. How many chromosomes are present for a fruit fly cell in G2 of the cell cycle? How many chromatids? |
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Definition
8 chromosomes
16 chromatids |
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Term
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Definition
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis |
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Term
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Definition
| chromosomes condense, and spindle apparatus begins to form; has 8 chromosomes and 16 chromatids |
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Term
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Definition
| nuclear envelope breaks down; microtubules contact chromosomes at kinetochores; 8 chromosomes and 16 chromatids |
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Term
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Definition
| chromosomes complete migration to middle of cell; 8 chromosomes and 16 chromatids |
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Term
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Definition
| sister chromatids separate into daughter chromosomes and are pulled to opposite poles of the spindle apparatus; 16 chromosomes |
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Term
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Definition
| the nuclear envelope re-forms, and chromosomes de-condense; 16 chromosomes |
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Term
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Definition
| actin-myosin ring causes the plasma membrane to begin pinching in; two daughter cells form; 8 chromosomes per cell |
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Term
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Definition
process in which prokaryotic cells (bacteria cells) divide
-DNA is copied and protein filaments attach
-DNA copies are separated; ring of protein forms
-ring of protein draws in membrane
4) fission is complete |
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Term
| Explain how the appearance of chromosomes is different for a cell in mitosis compared to a cell in interphase |
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Definition
| The chromosomes are condensed and easier to see during mitosis |
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Term
| Explain how chromosomes become attached to kinetochore microtubules (spindle fibers) during prometaphase. |
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Definition
| Each sister chromatid has its own kinetochore, which is assemble at the centromere. Since the centromere is also the attachment site for chromatids the results is two kinetochores on opposite sides of each replicated chromosome. Then kinesin and dynein motors are recruited to the kinetochore, where they can "walk" the chromosome up and down microtubules |
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Term
| When does the cell enter into metaphase? |
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Definition
| Once the kinetochore microtubules have moved all the chromosomes to the middle of the spindle, the mitotic cells enter metaphase |
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Term
| What causes the movement of the chromosomes toward opposite spindle poles during anaphase of mitosis? |
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Definition
| First, the daughter chromosomes move to opposite poles via the attachment of kinetochore proteins to the shrinking kinetochore microtubules. Second, the two poles of the spindle are pushed and pulled farther apart. Different motors on the membrane walk along on the astral microtubules to pull the poles to opposite sides of the cell |
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Term
| Describe the experiment shown in Figure 12.6. How did the results of this experiment aid in our understanding of what occurs during anaphase? |
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Definition
| This result suggested that the kinetochore microtubules remain stationary during anaphase, but shorten because tubulin subunits are lost from their plus ends. As microtubule ends shrink back to the spindle poles, the chromosomes are pulled apart |
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Term
| Cytokinesis in plant cells |
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Definition
| In plants, polar microtubules left over from the spindle help define and organize the region where the new plasma membranes and cell walls will form. Vesicles from the Golgi apparatus carry components to build a new cell wall to the middle of the dividing cell (via motor proteins). In the middle of what was the spindle, the vesicles start to fuse together to form a flattened sac-like structure called the cell plate. The cell plate continues to grow as new vesicles fuse with it, eventually contacting the existing plasma membrane. When the cell plate fuses with the existing plasma membrane, it divides the cell into two new daughter cells. |
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Term
| Cytokinesis in animal cells |
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Definition
| b. In animals, cytokinesis begins with the formation of a cleavage furrow. The furrow appears because a ring of actin filaments forms just inside the plasma membrane, in the middle of what used to be the spindle. As myosin moves the ring of actin filaments on the inside of the plasma membrane, the ring shrinks in size and tightens. Because the ring is attached to the plasma membrane, the shrinking ring pulls the membrane with it. As a result, the plasma membrane pinches inward. The actin and myosin filaments continue to slide past each other, tightening the ring further, until the original membrane pinches in two and cell division is complete. |
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Term
| T/F: M-phase cytoplasm DOES NOT contain a regulatory molecule that induces M phase in interphase cells |
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Definition
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Term
| Cyclin is at its _________ concentration in the cell cycle when it is entering M-phase |
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Definition
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Term
| How is the concentration of cyclin related to MPF activity? |
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Definition
| MPF is dependent (heavily) on the concentration of cyclin |
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Term
| Cdk (cyclin dependent kinase) |
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Definition
| catalyzes phosphorylation of other proteins to start M-phase |
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Term
| T/F: A dimer consisting of cyclin and a cyclin-dependent kinase activates MPF |
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Definition
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Term
| When MPF is active, what targets get phosphorylated by MPF? How does this cause the cell to enter M-phase? |
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Definition
| The phosphorylation of one site in Cdk activates the kinase, but when the second site is phosphorylated, it is inactivated. Both these sites are phosphorylated after cyclin binds to the Cdk. This allows the concentration of the dimer to increase without prematurely starting M phase. |
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Term
| G1 checkpoint passes if... |
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Definition
-cell size is adequate
-nutrients are sufficient
-social signals are present
-DNA is undamaged |
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Term
| G2 checkpoint passes if... |
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Definition
-chromosomes have replicated successfully
-DNA is undamaged
-activated MPF is present |
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Term
| M-phase checkpoint passes if |
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Definition
-chromosomes have attached to spindle apparatus
-chromosomes have properly segregated and MPF is abesent |
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Term
| In general, what is the purpose of cell cycle checkpoints? |
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Definition
| Interactions among regulatory molecules at each checkpoint allow a cell to "decide" whether to proceed with division or not. If these regulatory molecules are defective, the checkpoint may fail and cells may start dividing in an uncontrolled fashion |
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Term
| Why is the M-phase checkpoint important? |
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Definition
| If the metaphase checkpoint did not exist, some chromosomes might not separate correctly, and daughter cells would receive either too many or too few chromosomes |
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Term
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Definition
-arise from cells in which cell-cycle checkpoints have failed
-have defects that make the proteins required for cell growth active when they shouldn't be
-have defects that prevent tumor suppressor genes from shutting down the cycle |
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Term
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Definition
| a mass of abnormal tissue that appears due to unregulated growth but does not spread to other organs; not cancerous |
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Term
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Definition
| a tumor that is actively growing and disrupting local tissues or is spreading to other organs; cancer consists of one or more malignant tumors |
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Term
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Definition
| the spread of cancerous cells from their site of origin to distant sites in the body where they may establish additional tumors |
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Term
| What are three traditional methods of cancer treatment? |
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Definition
-Radiation
-Chemotherapy
-Surgery |
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Term
| Which statement about the daughter cells following mitosis and cytokinesis is correct? |
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Definition
| They are genetically identical with each other and with the parent cell |
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Term
| Progession through the cell cycle is regulated by oscillations in the concentration of which type of molecule? |
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Definition
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Term
| After the S phase, what comprises a single chromosome? |
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Definition
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Term
| What major events occur during anaphase of mitosis? |
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Definition
| Sister chromatids separate, and the spindle poles are pushed farther apart |
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Term
| What evidence suggests that during anapahse, kinetochore microtubules shorten at the kinetochore? |
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Definition
| Daughter chromosomes were observed to move toward the pole faster than do the marked regions of fluorescently labeled kinetochore microtubules |
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Term
| Under normal conditions, what happens to the cell cycle if the chromosomes fail to separate properly at anaphase? |
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Definition
| The cycle would arrest in M phase, and cytokinesis would not occur |
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Term
| Identify at least two events in the cell cycle that must be completed successfully for daughter cells to share an identical complement of chromosomes |
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Definition
| For daughter cells to have identical complements of chromosomes, all the chromosomes must be replicated during the S phase, the spindle apparatus must connect with the kinetochores of each sister chromatid in prometaphase, and the sister chromatids of each replicated chromosome must be partitioned in anaphase and fully separated into daughter cells by cytokinesis |
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Term
| Explain how microinjection experiments supported the hypothesis that specific molecules in the cytoplasm are involved in the transition from interphase to M phase. What was the control for this experiment? |
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Definition
| Microinjection experiments suggested that something in the cytoplasm of M-phase cells activated the transition from interphase to M phase. The control for this experiment was to inject cytoplasm from a G2 arrested oocyte. |
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Term
| Why are cyclins called cyclins? Explain their relationship to MPF activity. |
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Definition
| Cyclin concentrations change during the cell cycle. At high concentration, cyclins bind to a specific cyclin-dependent kinase (Cdk), forming a dimer. This dimer becomes active MPF by changing its shape through the phosphorylation (activating site) and de-phosphorylation (inhibitory site) of Cdk. |
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Term
| In multicellular organisms, nondividing cells stay in G0 phase. For the cell, why is it better to be held in G1 rather than S, G2, or M phase? |
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Definition
| G1 cells have not replicated their DNA in preparation for division |
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