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Cell Cycle Terminology

MitosisChromosomeChromatidSpindle CentrioleCentromereKinetochorePhases of the Cell Cycle

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Cell CycleLife Science: Molecular

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Limits to Cell Growth

There are two main reasons why cells divide rather than continue to grow indefinitely.

As a cell grows larger…1. More demand is placed on the DNA to create more

cell parts.2. It becomes harder to move enough nutrients in and

wastes out of the cell membrane.

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Cell CycleDuring the cell cycle a cell grows, prepares for division, and divides to form two daughter cells.

Interphase is the time between cell division. ● G1 (cell growth).● S phase is when DNA is copied.● G2 (cell growth).

Mitosis cell division.

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Cell Cycle

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Cell Division

Mitosis is the process of a cell dividing to form two identical daughter cells.Before dividing a cell replicates all of its DNA so that each daughter cell will get a complete set of “genetic information”.

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Stages of Mitosis

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Mitosis

Biologists divide the events of mitosis into four phases: prophase, metaphase, anaphase, and telophase.

How long does mitosis take?Typically mitosis takes about 80 minutes in eukaryotic cells. Depending on cell type mitosis may last anywhere from a several minutes, to several days.

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Chromosomes

A chromosome is a compact form of DNA that is visible only during cell division.A chromatid is one of two identical parts of a duplicated chromosome.

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Chromatids

The centromere is the part of a chromosomes where two sister chromatids are connected.A kinetochore is a protein structure that forms at the centromere of DNA during mitosis.

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The spindle is a microfilament structure that separates chromosomes during cellular division. The centrioles are microtubule structures that organize the spindle during cellular division.

Spindle

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Prophase

Prophase is the first and longest phase of mitosis.● The DNA condenses into chromosomes.● The nucleolus disappears● The nuclear envelope breaks down.

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Prometaphase

Prometaphase is an intermediate step after prophase, but before metaphase.

● Centrioles separate and take up positions on opposite sides of the nucleus.

● Spindle fibers emerge from the centrioles and connect to the chromatids.

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Metaphase

Metaphase is the second phase of mitosis.● Chromosomes line up in the middle of the cell.● Spindle fibers connect the kinetochore of each

chromatid to the centrioles.

Meta means “middle”

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Anaphase

Anaphase is the third phase of mitosis.● Sister chromatids separate.● Chromosomes are pulled to opposite ends of the

cell.● Anaphase ends when the chromosomes stop

moving.

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Telophase

Telophase is the fourth phase of mitosis.● The nuclear envelope re-forms. ● The chromosomes unwind back into chromatin. ● The nucleolus becomes visible again.

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Cytokinesis

Cytokinesis is the splitting of the cell, which usually occurs at the same time as telophase.In animal cells, cytokinesis results when a protein ring called actin contracts pinching the cell into two daughter cells.

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Animal Cell Cytokinesis

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Plant Cell Cytokinesis

In plant cells, a rigid cell wall requires that a cell plate be built between the two daughter cells.

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Mitosis Activity