bio flash cards mitosis

8/3/2019 Bio Flash Cards Mitosis

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What is the Miotic Spindle?


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The structure that directs chromosome movement during division.

Formed from microtubules that originally composed the Cytoskelet

Other cytoskeletal microtubules disassemble

during mitosis. Possibly providing raw

material (tubulin) for the spindle.

Assembly begins at the centrosome.Earlyin mitosis, the centrosome replicates and then one centrosome migrato each pole. Centrioles may be important


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What is the purpose of the Miotic

Spindle?


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The fibers of the spindle connect either to:

1. the individual sisterchromatids

2. microtubules from theother pole of the cell.

Each individual chromatid will be connected to a spindle fiber. A

spindle fiber attaches to a kinetochore region at the centromere.


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What is the role of Interphase in the ce

cycle?


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Interphase = 90% is divided into three phases:

G1 Phase: First Gap - The cell grows by producing proteins and cytoplasm

organelles.

S Phase: DNA Synthesis - The cell duplicates

its chromosomes; Continues to grow by

producing proteins and cytoplasmic organelles.

G2 Phase: Second Gap - The cell grows by

producing proteins and cytoplasmic organelles.


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How large of a part does Mitosis play i

the cell cycle?


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Mitosis = 10% of the cell cycle & consists of 5 sub-phases:

1. Prophase2. Prometaphase3. Metaphase4. Anaphase5. Telophase


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Describe the cells state in Late

Interphase


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Nucleus is well defined &surrounded by nuclear envelope

Nucleoli present in the nucleus Centrosome has replicated Microtubules extend from the

centrosomes in radial arrays

called asters (stars)

Chromosomes replicated; notobserved

Chromatin still loosely packed


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Describe the cells state in Prophase


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Chromatin condenses intochromosomes

The centrosomes are tightlycoiled, with sister chromatids

joined together The nucleoli disappear The miotic spindle begins to

form Centrosomes push away from

each other toward opposite ends

(poles) of the cell


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Describe the cells state in Prometapha


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The nuclear envelopefragments (stows in RER)

Centrosomes reach thepoles

Spindle fibers interact withthe chromosomes

Fibers from each poleattach to kinetochores Non-kinetochore fibers

from the opposite pole


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Describe the cells state in Metaphase


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Spindle is Completely formed Sister chromatids line up at

the center of the cell

(Metaphase Plate)

One chromatid sits on eachside of the metaphase plate

Each Chromatid is attached toopposite spindle poles


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Describe the cells state in Anaphase


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Sister chromatids separate and arenow considered chromosomes

New chromosomes migrate to thepoles

Kinetochore microtubules shortenas chromosome migrate

Non-kinetochore microtubuleslengthen, pushing the poles apart

By the end of anaphase, the twopoles have equivalent sets of

chromosomes


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Describe the cells state in Telophase


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At telophase, the cellcontinues to elongate as

spindle fibers from eachCentrosome push off each

pair

Two nuclei begin to formfrom fragments of parent

cells nuclear envelope

Chromatin becomes lesstightly coiled

Cytokinesis, division of thecytoplasm begins


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Describe Cytokinesis in Animals


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On the cytoplasmic side ofthe cleavage furrow a

contractile ring of actin

microfilaments and the motor

protein myosin form.

Contraction of the ringpinches the cell in two.


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Describe Cytokinesis in Plants


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During telophase, vesicles fromthe Golgi gather at the metaphase

plate, forming a cell plate.

The cell plate enlarges. Membranes fuse with the

plasma membrane

The contents of the vesicles formnew wall material in between.


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How do Bacterial Cells Reproduce?


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How is the Cell Cycle Regulated?


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The cell cycle contains checkpoints. The checkpoint stops the cell c

until all of the conditions necessary to proceed have been met. Ther

are 3 checkpoints:

End ofG1 End ofG2 End ofMetaphaseIf a cell does not receive all ofthe correct signals, it may

switch to a G0 or non-dividing

phase.


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What is responsible for Cell Cycle

Regulation


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The cell cycle is regulated by sets of molecules that both trigger and

coordinate key events of the cell cycle.


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What is the purpose/effects of Activate

MPF?


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What are internal regulators?


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Internal: a signal is released from kinetochores that are not

bound to fibers.

Blocks anaphase.


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What are external regulators?


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External: a variety of external chemical and environmentalconditions regulate division.

Growth factors are chemicals that must be present forsome cells to divide. blood cells

Density-dependent inhibition occurs when most cellsbecome crowded. Factors are limited.

Anchorage dependence occurs when a cell will not diviunless it is attached to something. (most animal cells)


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Cancer


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Cancer occurs when cell division escapes regulation.

Cancerous cell division occurs indefinitely.


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Cancer Progression


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Cancer Progression:

A single cell in a tissue undergoes transformation into a cancer ce If the immune system does not catch the changed cell, it will divi

repeatedly and form a tumor.

If the tumor remains in the same spot it is called benign and canusually be removed with surgery.

If the tumor spreads and invades other tissues it is called malign If the cancer cells spread to other parts of the body via lymph or

blood then the cancer has metastasized (metastasis).

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