Transcript Cell Cycle & Cell Division

The Cell
Cycle
1
Cell Division
• All cells are derived from preexisting cells
• Eukaryote cells divide to make
cells for growth and to replace
damaged or old cells
• Prokaryote cells divide to
reproduce
2
Eukaryotic Chromosomes
• Human body cells have 46 chromosomes
or 23 matching pairs
• Each chromosome is composed of a
single, tightly coiled DNA molecule
3
Chromosomes in Dividing Cells
• Duplicated
chromosomes are
called
chromatids &
are held
together by the
centromere
Called Sister Chromatids
4
Karyotype
• A picture of the
chromosomes from
a human cell
arranged in pairs by
size
• First 22 pairs are
called autosomes
• Last pair are the
sex chromosomes
• XX female or XY
male
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Cell Reproduction
6
Types of Cell Reproduction
• Asexual reproduction
involves a single cell
dividing to make 2 new,
identical daughter cells
• Examples: Mitosis & binary
fission
7
• Sexual reproduction involves
joining two cells (egg & sperm).
• Example: Meiosis
• Fertilization involves joining of
egg & sperm to make a new cell
(zygote)
8
Cell Division in
Prokaryotes
9
Cell Division in Prokaryotes
• Prokaryotes such as
bacteria divide into 2 Parent
cell
identical cells by the
process of binary
fission
Chromosome
replicates
Cell splits
2 identical
daughter cells
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The Cell
Cycle
11
Five Phases of the Cell Cycle
1. G1 - primary growth phase
2. S – synthesis; DNA replicated
3. G2 - secondary growth phase
collectively these 3 stages are
called interphase
4. M - mitosis
5. C - cytokinesis
12
Interphase
13
Interphase - G1 Stage
• 1st growth stage after cell
division
• Cells mature by making more
cytoplasm & organelles
• Do all the work of being a cell
in this stage
14
Interphase – S Stage
• Synthesis stage
• DNA is copied or replicated
Two
identical
copies
of DNA
Original
DNA
15
Interphase – G2 Stage
• 2nd Growth Stage
• Occurs after DNA has been
copied
• All cell structures needed for
division are made (EX: cell
organelles & centrioles)
16
The Cell Cycle
DNA Copied
Cells
Mature
Daughter
Cells
Cells prepare for
Division
Cell Divides into
Identical cells
17
Mitosis
18
Mitosis
• Division of the
nucleus
• Only occurs in
eukaryotes
• Doesn’t occur in
brain or muscle
cells
19
Four Mitotic Stages
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
20
Prophase
• Chromatin in nucleus condenses to
form visible chromosomes
• Nuclear membrane & nucleolus are
broken down
• Centrioles move in animal cells
21
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Metaphase
• Chromosomes move to the center of
the cell
• Chromosomes are now lined up at the
equator
Equator of Cell
Pole of
the Cell
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Metaphase
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Anaphase
• Occurs rapidly
• Sister
chromatids are
pulled apart to
opposite poles
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Anaphase
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Telophase
• Sister chromatids are at opposite
poles
• Nuclear envelope forms around
each set of sister chromatids
• Nucleolus reappears
27
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Cytokinesis
• Means division of the cytoplasm
• 1 Cell
two identical cells
• In plant cells; cell plate forms
at the equator to divide cell
• In animal cells; cleavage furrow
forms to split cell
• Chromosome structures dissolve
into chromatin
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Cytokinesis
Cleavage furrow
in animal cell
Cell plate in
plant cell
30
Review
of
Mitosis
31
Eukaryotic Cell Division
• Used for growth and
repair
• Produce two new cells
identical to the original
cell
• Cells are diploid (2n)
Prophase
Metaphase
Chromosomes during
Metaphase of mitosis
Anaphase Telophase Cytokinesis
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Locate the Four Mitotic
Stages in Plants
Anaphase
Telophase
Metaphase
Prophase
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anaphase
prophase
metaphase
telophase
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Uncontrolled Mitosis
• If mitosis is not
controlled, unlimited
cell division occurs
causing cancerous
tumors
• Oncogenes - special
proteins that
increase the chance
that a normal cell
develops into a tumor
cell
Cancer cells
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