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Chapter 10-2
• Chromosomes are not visible in cells until
cells begin the process of cell division.
• Chromosomes consist of two identical
sister chromatids.
• A centromere holds the two sister
chromatids together at their centers.
• Cell Cycle
• The cell goes through a stage called
interphase between cell divisions.
• Cells grow and then divide in a series
of events called the cell cycle.
• M phase is the when the nucleus divides.
• Interphase consists of:
• G phase
1
• S phase
• G phase
2
• G phase - cells do most of their growing.
1
• S phase
• G phase
2
Mitosis
• Four phases:
–Prophase
–Metaphase
–Anaphase
–Telophase
Mitosis
• Centrioles are the tiny structures located
in the cytoplasm near the nuclear
envelope at the beginning of prophase.
Mitosis
• Spindle – is the fanlike microtuble
structure that helps separate the
chromosomes.
Mitosis
• During Prophase:
•
• the chromosomes become visible in the
nucleus;
• the centrioles take up positions on
opposite sides of the nucleus.
Mitosis
• During Metaphase:
• The chromosomes line up in the center of
the cell.
Mitosis
• During Anaphase :
• The chromosomes move until they form
two separate
• Forming groups at opposite poles of the
spindle.
Mitosis
• During Telophase:
• the nuclear envelope re-forms around
each cluster of chromosomes;
• the nucleolus becomes visible in each
daughter nucleus.
Cytokinesis
• Cytokinesis is the division of the
cytoplasm.
Cytokinesis
• How does it happen in animals?
• The membrane is drawn downward until it
is pinched into nearly two equal parts.
Cytokinesis
• A cell plate is formed midway between
the divided nucleus during cytokinesis in
plant cells.