Why do some species employ both mitosis and meiosis, whereas other species use only mitosis?
answer
A single-celled organism only needs mitosis.
They need only mitosis to make large numbers of cells such as sperm.
* They need both if they are producing animal gametes.*
They need meiosis if the cells are producing organs such as ovaries.
They need only meiosis if they produce egg cells.
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DNA replication produces two identical DNA molecules, called __________, which separate during mitosis.
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Sister chromatids
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After chromosomes condense, the __________ is the region where the identical DNA molecules are most tightly attached to each other.
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Centromere(s)
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During mitosis, microtubules attach to chromosomes at the ________.
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Kinetochore(s)
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In dividing cells, most of the cell's growth occurs during _________.
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Interphase
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The _________________ is a cells structure consisting of microtubules, which forms during early mitosis and plays a role in cell division.
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Mitotic spindle(s)
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During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called ________.
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Chromatin
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In most eukaryotes, division of the nucleus is followed by ____________; when the rest of the cell divides.
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Cytokinesis
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The ____________ are the organizing centers for microtubules involved in separating chromosomes during mitosis.
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centrosome(s)
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G1 Phase
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Non-diving cells exit cell cycle
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G1 Checkpoint
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At this point, cell commits to go through the cycle
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S Phase
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DNA replication
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G2 Phase
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Centrosome replicates
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M Phase
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Mitotic spindle begins to form
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M Checkpoint
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Cell divides, forming two daughter cells
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Are sister chromatids present in all or part of this phase:
G1
S
G2
Beginning of M( Prophase -> early Anaphase)
End of M (late Anaphase -> telophase)
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No
Yes
Yes
Yes
No
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Is the DNA condensed in all or part of this phase?
G1
S
G2
Beginning of M( Prophase -> early Anaphase)
End of M (late Anaphase -> telophase)
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No
No
No
Yes
Yes
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Does the cell contain twice as much DNA in this phase as it did in the G1 phase?
G1
S
G2
Beginning of M( Prophase -> early Anaphase)
End of M (late Anaphase -> telophase)
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No
Yes
Yes
Yes
Yes
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Prophase
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Cohesin join sister chromatids of duplicated chromosomes.
Tubulins assumble into spindle microtubules
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Prometaphase
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Microtubules attack to kinetochores.
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Metaphase
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Kinetochores are motionless in relation to poles of cell
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Anaphase
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Cohesins break down.
Kinetochores move toward poles of cell.
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Telophase
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Spindle microtubules disassemble.
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During prophase, the microtubules of the mitotic spindle ______.
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Lengthen
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During anaphase, the nonkinetochore microtubules _______ and move past each other, and the kinetochore microtubules _________.
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Lengthen , Shorten
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During telophase, the nonkinetochore microtubules _________.
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Disassemble
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Diagram showing the motor protein of a kinetochore, whose function has been blocked due to the effect of an inhibitor.
Will this cell elongate during mitosis?
Will the sister chromatids separate from each other?
Will the chromosomes move to the poles of the cells?
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Yes
Yes
No
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Bacteria only
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Chromsome separation begins at the origin of replication on DNA
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Eukaryotes only
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Before seperation, duplicated chromosomes condense.
Nuclear envelope fragments, permitting chromosome separation.
Two copies of the duplicated chromosomes are attached at their centromeres before separating.
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Both bacteria and eukaryotes
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Replicated chromosomes seperate by attaching to some other structural feature of the cell.
Chromosomes replicate before cell division.
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Cytokinesis in animal cells is accomplished by constriction of the cell along the plane of cell division (formation of a cleavage furrow). In plant cells, which have cell walls, a completely different mechanism of cytokinesis has evolved.
Which of the following statements are true of cytokinesis in plant cells? Select the two that apply.
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After chromosome separation is complete, a network of microfilaments forms near the plane of cell division that will separate the two new cells.
* Vesicles from the Golgi apparatus move along microtubules, coalesce at the plane of cell division, and form a cell plate.
The cell plate consists of the plasma membrane and cell wall that will eventually separate the two daughter cells.*
The plasma membrane of the parent cell grows inward, eventually joining with the cell plate
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Cell divide by constriction of a ring of protein.
Bacteria
Animals
Plants
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True
True
False
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The presence of cell wall prevents the cell from dividing by constriction.
Bacteria
Animals
Plants
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False
False
True
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Tubulin or tubulin-like molecules function in binary fission (in bacteria) or cytokinesis (in animals and plants).
Bacteria
Animals
Plants
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True
False
True
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Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?
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formation of the cell plate
binary fission
formation of the mitotic spindle
*cleavage*
DNA replication
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Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle?
Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle?
