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Copyright Pearson Prentice Hall

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Prentice HallBiology


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10-2 Cell Division


10-2 Cell Division

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In eukaryotes, cell division occurs in two major stages.

The first stage, division of the cell nucleus, is called mitosis.

The second stage, division of the cell cytoplasm, is called cytokinesis.


10-2 Cell Division

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Chromosomes

Chromosomes

Genetic information is passed from one generation to the next on chromosomes.

Before cell division, each chromosome is duplicated, or copied.


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Chromosomes

Each chromosome consists of two identical “sister” chromatids.

Each pair of chromatids is attached at an area called the centromere.

Sister chromatids

Centromere


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Chromosomes

When the cell divides, the chromatids separate.

Each new cell gets one chromatid.


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The Cell Cycle

What are the main events of the cell cycle?


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The Cell Cycle

The Cell Cycle

The cell cycle is the series of events that cells go through as they grow and divide.

Interphase is the period of growth that occurs between cell divisions.


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The Cell Cycle

During the cell cycle:

• a cell grows

• prepares for division

• divides to form two daughter cells, each of which begins the cycle again


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The Cell Cycle

The cell cycle consists of four phases:

• G1 (First Gap Phase)

• S Phase

• G2 (Second Gap Phase)

• M Phase


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Events of the Cell Cycle


During G1, the cell

• increases in size

• synthesizes new proteins and organelles


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During the S phase,

• chromosomes are replicated

• DNA synthesis takes place

Once a cell enters the S phase, it usually completes the rest of the cell cycle.


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The G2 Phase (Second Gap Phase)

• organelles and molecules required for cell division are produced

• Once G2 is complete, the cell is ready to start the M phase—Mitosis


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Cell Cycle



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Mitosis

What are the four phases of mitosis?


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Mitosis

Mitosis

Biologists divide the events of mitosis into four phases:

• Prophase

• Metaphase

• Anaphase

• Telophase


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Mitosis

Mitosis


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Section 10-2ProphaseSpindle

forming

Chromosomes (paired

chromatids)Centromere

Click to Continue

Mitosis

Prophase


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Mitosis

Prophase

Prophase is the first and longest phase of mitosis.

The centrioles separate and take up positions on opposite sides of the nucleus.

Spindle forming

CentromereChromosomes(paired chromatids)


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Mitosis

The centrioles lie in a region called the centrosome.

The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes.

Spindle forming



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Mitosis

Chromatin condenses into chromosomes.

The centrioles separate and a spindle begins to form.

The nuclear envelope breaks down.

Spindle forming



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Centriole

Centriole

Spindle

Mitosis

Click to Continue

Metaphase

Metaphase


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Mitosis

Metaphase

The second phase of mitosis is metaphase.

The chromosomes line up across the center of the cell.

Microtubules connect the centromere of each chromosome to the poles of the spindle.

Centriole

Spindle


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Individual chromosomes

Anaphase

Mitosis

Anaphase


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Mitosis

Anaphase

Anaphase is the third phase of mitosis.

The sister chromatids separate into individual chromosomes.

The chromosomes continue to move until they have separated into two groups.

Individualchromosomes


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Nuclear envelope reforming

Telophase

Mitosis

Telophase


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Mitosis

Telophase

Telophase is the fourth and final phase of mitosis.

Chromosomes gather at opposite ends of the cell and lose their distinct shape.


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Mitosis

A new nuclear envelope forms around each cluster of chromosomes.


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Cytokinesis

Cytokinesis

Cytokinesis


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Cytokinesis

During cytokinesis, the cytoplasm pinches in half.

Each daughter cell has an identical set of duplicate chromosomes.


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Cytokinesis

In plants, a structure known as the cell plate forms midway between the divided nuclei.

Cell wallCell plate


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Cytokinesis

The cell plate gradually develops into a separating membrane.

A cell wall then begins to appear in the cell plate.


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10-2


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10-2

The series of events that cells go through as they grow and divide is called

a. the cell cycle.

b. mitosis.

c. interphase.

d. cytokinesis.


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10-2

The phase of mitosis during which the chromosomes line up across the center of the cell is

a. prophase.

b. metaphase.

c. anaphase.

d. telophase.


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10-2

Cytokinesis usually occurs

a. at the same time as telophase.

b. after telophase.

c. during interphase.

d. during anaphase.


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10-2

DNA replication takes place during the

a. S phase of the cell cycle.

b. G1 phase of the cell cycle.

c. G2 phase of the cell cycle.

d. M phase of the cell cycle.


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10-2

During mitosis, “sister” chromatids separate from one another during

a. telophase.

b. interphase.

c. anaphase.

d. metaphase.

END OF SECTION

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