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Glossary Main Men u Cell Cycle Interpha se Cytokines is Mitosis What Is I t? Why Do We Ne ed It? Cellular Structure s Glossar y Mitosis A nimation

GlossaryMain Menu Cell Cycle Interphase Cytokinesis Mitosis What Is It? Why Do We Need It?Why Do We Need It? Cellular Structures Glossary Mitosis Animation

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GlossaryMain Menu

Cell Cycle

Interphase

Cytokinesis

Mitosis

What Is It? Why Do We Need It?

Cellular Structures Glossary

Mitosis Animation

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The Cell Cycle The Cell Cycle

The cell cycle is the sequence of growth and division of a cell. It consists of three major

phases: Interphase, mitosis, and cytokinesis. Cell division results in two cells that are both

identical to the parent cell.

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Why do cells grow and Why do cells grow and divide?divide?

All cells come from other cells. As organisms grow and change (a growing

vine, or a tadpole changing to a frog) new cells need to be produced. Cell growth and division also allows worn-

out tissues to be repaired and/or replaced.

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Mitosis AnimationMitosis Animation

Mitosis

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InterphaseInterphase

Interphase is the phase where the cell spends the majority of its life. During interphase, the cell grows,

carries on metabolism, and chromosomes are duplicated to form sister chromatids in order to prepare

for cellular division.

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MitosisMitosis

Mitosis is the phase where nuclear division takes place and the cell

divides. Mitosis occurs in a sequence of 4 stages: Prophase,

metaphase, anaphase, and telophase.

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CytokinesisCytokinesis

Cytokinesis is the final phase of the cell cycle. This is where the

cytoplasm divides. In animals, the plasma membrane pinches along the equator of the cell. In plants, the cell plate is laid down across the equator and new cell walls form on each side.

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ProphaseProphaseProphase is the longest of the mitotic stages. During prophase, four major

cellular changes take place:• Chromatin coils to form visible

chromosomes.• The nucleus begins to disappear.• Centrioles migrate to opposite ends of the

cell.• Spindle fibers begin to form.

Mitosis

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MetaphaseMetaphase

Metaphase is a shorter mitotic stage. Several things occur during

metaphase…

Mitosis

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Metaphase…Metaphase…

First, chromosomes begin to move to the equator of the spindle.

Mitosis

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Metaphase…Metaphase…

Each sister chromatid attaches to a separate spindle fiber via its

centromere.

Mitosis

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Metaphase…Metaphase…

These spindle fibers extend from opposite poles. This ensures that each

new cell receives an identical and complete set of chromosomes.

Mitosis

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Metaphase…Metaphase…

When metaphase is complete, the spindle has formed completely and the sister chromatids are attached along the equator of the spindle.

Mitosis

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AnaphaseAnaphaseDuring anaphase, the centromeres split, and sister chromatids migrate

to opposite poles of the cell.

Mitosis

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TelophaseTelophaseTelophase is the final stage of mitosis.

The chromotids have now reached the poles of the cell and unwind into

chromosomes. This allows metabolic activity to recommence.

Mitosis

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Telophase…Telophase…Many of the processes that occurred

during prophase reverse themselves.

Mitosis

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Telophase…Telophase…• The spindle fibers break down

• The nucleolus reappears• The nuclear envelope forms

• Two nuclei now exist that are identical to the nucleus of the parent cell.

Mitosis

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GlossaryGlossary• centriole• centromere• chromatid• chromatin• chromosome• nuclear envelope• nucleolus• nucleus• spindle• spindle fiber

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centriolecentrioleA centriole is a barrel microtuble structure

found in most animals cells. Two centrioles arrange themselves

perpendicularly to form a centrosome. Centrioles organize the mitotic spindle upon which chromosomes are pulled

apart during cellular division.

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centromerecentromereThe centromere is a region of the

chromosome where the spindle fibers of the mitotic spindle attach. The

centromere is also the point of attachment of the two sister chromatids

once a chromosome has been duplicated for cellular division.

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chromatidchromatidA chromatid is one strand of the

chromosome after it has duplicated for cellular division. The two chromatids are called “sister chromatids” and will eventually split and move to opposite

ends of the cell.

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chromatinchromatin

Chromatin is the building block for a chromosome. It is only made visible by

staining. It consists of DNA and proteins. When the cell prepares to

divide, the chromatin thickens and can be seen as distinct chromosomes.

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chromosomechromosome

A chromosome is a long, continuous piece of DNA which contains the

genetic information for a cell.

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nuclear nuclear envelopeenvelope

The nuclear envelope is the double membrane of the nucleus in eukaryotic cells. It separates the contents of the

nucleus from the cytosol.

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nucleolusnucleolus

The nucleoulus is a “suborganelle” of the nucleus. It refers to a “knot” of

chromatin located within the nucleus. No membrane surrounds the nucleolus.

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nucleusnucleus A nucleus is found in all eukaryotic cells.

It is a structure that contains the cell’s genetic material. The nucleus controls chemical reactions that take place in the cytosol, regulates expression of

genes, and stores information needed for cellular division. The nucleus is

surrounded by a membrane called the nuclear envelope.

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spindlespindle

The mitotic spindle is a network of microtubules that is formed during the

prophase stage of mitosis.

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spindle fiberspindle fiberA spindle fiber is one of the microtubules

comprising the mitotic spindle. Some of these spindle fibers attach to the

centromeres of the chromosomes and help draw the chromatids apart during

anaphase.