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Prentice Hall Biology
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10-2 Cell Division
Photo Credit: © CAMR/A.B. Dowsett/Science Photo Library/Photo Researchers, Inc.
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Cell Division
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.
Mitosis – 4 phases
Division- 2 stages
Cell Cycle- Cell Life cycle
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4. Before cell division, each chromosome is duplicated, or copied.
Chromosomes
Before cell division, each chromosome is duplicated, or copied.
Review DNA, chromosome, gene
DNA = book
Chromosome = chapter
Gene= paragraph
Sister Chromatid= copies of the same book
Supercoiling- why it is thick and not stringy.

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Chromosomes
Chromosomes
Genetic information is passed from one generation to the next on chromosomes.
Every living organism has a specific number of chromosomes:
humans : 46
fruit flies: 8
carrots: 18
this is called the organisms DIPLOID NUMBER (2n)
Discuss X and Y at this point. It will be revisited in sex-linked traits but students should see the 23rd pair is the sex chromosomes which determine gender. This will also be needed information for the coin toss lab.
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Chromosomes
Discuss the X shape- duplicated which makes it ready for division
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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.
When the cell divides, the chromatids separate.
Each new cell gets one chromatid.
Sister chromatids
Photo Credit: © Gunther F. Bahr/AFIP/Stone
Each cell gets a complete copy of the infomration
Centromere
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The Cell Cycle
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.
INTERPHASE IS NOT PART OF MITOSIS!!!
MITOSIS IS PART OF THE CELL CYCLE
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9. Events of the Cell Cycle
During the cell cycle, the cell grows, replicates its DNA, and divides into two daughter cells. DNA synthesis takes place during the S phase. Cell division takes place during the M phase. G1 and G2 are gap phases.
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Mitosis
Mitosis
Biologists divide the events of mitosis into four phases: (PMAT)
Prophase (Pair)
Metaphase (Meet in the Middle)
Anaphase (Away)
Telophase (Tear)
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Mitosis
Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells.
Mitosis
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12. Chromosomes (paired chromatids)
Mitosis
Section 10-2
Spindle forming
Prophase
Prophase
Chromosomes (paired chromatids)
Centromere
Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells.
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Mitosis
Spindle
forming
Prophase
Prophase is the first and longest phase of mitosis.
The centrioles separate and take up positions on opposite sides of the nucleus.
Centromere
Chromosomes
(paired chromatids)
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Mitosis
Spindle
forming
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.
Centromere
Chromosomes
(paired chromatids)
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Mitosis
Spindle
forming
Chromatin condenses into chromosomes.
The centrioles separate and a spindle begins to form.
The nuclear envelope breaks down.
Centromere
Chromosomes
(paired chromatids)
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16. Homologous Chromosomes
During prophase the homologues (homologous chromosomes) pair up and find there match.
Mom gives a chromosome (red)
Dad gives a chromosome (blue)
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Mitosis
Metaphase
Centriole
Spindle
Centriole
Metaphase
Metaphase – the chromosomes meet in the middle
Indicate the alignment- this is important due to the change during meiosis and the chromosome set number (n)
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Mitosis
Centriole
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.
Spindle
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19. Individual chromosomes
Mitosis
Anaphase
Individual chromosomes
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.
Individual
chromosomes
Anaphase= the sister chromatids move away from each other to opposite ends
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21. Nuclear envelope reforming
Mitosis
Telophase
Nuclear envelope reforming
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.
A new nuclear envelope forms around each cluster of chromosomes.
Telophase: the cell begins to tear in half
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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
In plants, a structure known as the cell plate forms midway between the divided nuclei.
Cell plate
Cell wall
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10-2
- or -
(must have QuickTake software installed on the computer you are using for this presentation)
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10-2
The series of events that cells go through as they grow and divide is called
the cell cycle.
mitosis.
interphase.
cytokinesis.
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10-2
The phase of mitosis during which the chromosomes line up across the center of the cell is
prophase.
metaphase.
anaphase.
telophase.
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10-2
Cytokinesis usually occurs
at the same time as telophase.
after telophase.
during interphase.
during anaphase
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10-2
DNA replication takes place during the
S phase of the cell cycle.
G1 phase of the cell cycle.
G2 phase of the cell cycle.
M phase of the cell cycle.
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10-2
During mitosis, “sister” chromatids separate from one another during
telophase.
interphase.
anaphase.
metaphase.
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32. END OF SECTION