Transcript Mitosis and the Cell Cycle

Mitosis and the Cell
Cycle
Cell reproduction
Biology is the only
subject in which
multiplication is the
same thing as division…
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Why do cells divide…
 One-celled organisms
1.
for reproduction
amoeba
 Multi-celled organisms
1.
for growth & development

2.
from fertilized egg to adult
for repair & replacement

replace cells that die from
normal wear & tear or from injury
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starfish
The Cell Cycle---life cycle of a
cell
 The
sequence of growth and
division of a cell.
 The cell cycle occurs in a series
of stages, or phases
 95% of cell cycle is in
interphase
 5% of cell cycle is in mitosis
and cytokinesis
Interphase
 Stage
between cell division
Most of the cell’s life takes place in
Interphase
 Chromosome replication (their
number doubles)
Interphase continued—
the chromosmes become a pair of
chromatids and are held together
by a centromere
Centromere

This stage ends in preparation
for mitosis(dividing of the cell )
Stage 2 Mitosis
Happens
in all eukaryotic
cells
Cell division process
4 major stages or steps
 REMEMBER PMAT
Prophase
Prepare for cell division
Mitosis begins (cell begins to divide)
 1.Chromatin condenses to form X like
structures
 2.Spindle fibers form between the poles
 3.Nuclear membrane breaks down

duplicated chromosomes
(prophase)
cell
nucleus
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Metaphase
Meet
in the Middle
 Chromosomes
line up across
the middle of the cell with sister
chromatid at equator
 Spindle fibers attach to
centromere
metaphase
duplicated chromosomes
lined up in middle of cell
Anaphase
AWAY– the chromatids are pulled away
from each other.
 Centromeres
break
 Each chromatid is now a
separate chromosome
 Each chromosome is pulled to
each pole of the cell
anaphase
chromosomes split &
move to opposite ends
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Telophase
Tearing apart into Two cells.
Cell begins to pull in two
 Two new nuclear envelopes form and
surround each set of chromosomes
 Chromosomes unwind into long strands
 Last stage of mitosis

telophase
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3rd Stage Cytokinesis
 Cell
membrane pinches
down and divides the
cytoplasm
 Two new identical daughter
cells are formed
 In cells that have a cell wall a
cell plate forms between the
new cells and then becomes
the cell wall
Summary
Cell Cycle
1.Interphase—growing stage
2.Mitosis—dividing stage
4 Stages
a.Prophase—Preparing
b.Metaphase—Meeting the Middle
c.Anaphase—attachment changes
d.Telophase—Tearing into two
3.Final Process Cytokinesis-2 new
daughter cells