Download Meiosis

Mitosis & the Cell
Cycle
Cell Growth & Development
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Are cells of organisms the same size? Do your
cells get bigger as you grow, or do you just
produce more cells?
When talking about Cell Size…… Smaller is
Better!
The larger a cell becomes, the more demands
the cell places on its DNA, and the harder it is
to supply with nutrients.
Cell Division
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Before a cell becomes to large, a growing cell
will divide.
Cell division is the process by which a Single cell
divides into 2 Daughter cells.
Cell Division = the series of events that cells go
through as they grow and divide.
WHAT TO COPY
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COPY THE NOTES IN YELLOW
Chromosomes
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Chromosomes= are
composed of DNAWhich carries the cell’s
coded genetic
information.
Humans have 46
chromosomes(23 pairs).
The chromosomes
consist of two identical
sister chromatids.
Two Major Types of Cell Division
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Mitosis- Somatic cells
(Body Cells)
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Diploid 2N
Meiosis- Sex cells/
Gametes
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Haploid 1N
Mitosis
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Mitosis is the process by which the genetic
information is replicated and distributed to
daughter cells.
2 diploid(2N) daughter cells are produced from
1 diploid (2N) parent cell.
The Daughter cells are genetically identical to
the parent cell.
There are 4 major stages to mitosis, PMAT.
Mitosis does NOT include interphase.
Interphase
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Interphase= The cell spends most of its life
here; not part of the actual reproduction. NOT
PART OF MITOSIS.
Cell grows and replicates its DNA and centrioles.
 Nuclear membrane is visible
 Nucleus, Nucleolus, and chromatin can be seen.
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Interphase
Prophase
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Prophase: first phase of
Mitosis
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Nuclear membrane breaks
down
Chromosomes become
visible
 Centrioles separate
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Spindle forms
Metaphase
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Metaphase: Second part
of Mitosis
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Chromosomes attach to
spindle
Chromosomes line up
across the center of the
cell
Anaphase
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Anaphase: Third step in
Mitosis
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The sister chromatids
separate and move apart
towards opposite poles.
The chromatids are now
called chromosomes.
Telophase
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Telophase: Fourth stage
of Mitosis
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Chromosomes gather at
opposite ends of the cell
The nuclear membrane
begins to form and
enclose the chromosomes
Cell membrane begins
to move inwards
Cytokinesis
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Cytokinesis: Final stage in
cellular division
Not Mitosis
Works with telophase
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The cytoplasm divides
completely in half.
2 daughter cells with
identical genetic
information are produced.
MEIOSIS
Sex cells and gametes
 Meiosis
is the process by which
sex cells/ gametes are produced.
 These
sex cells are haploid (1N).
Number of Chromosomes
 Human
body cells have 46
chromosomes
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Human sex cells, sperm and
eggs, have 23 chromosomes.
Why should gametes have only half
the number of normal
chromosomes???
 During
meiosis, FOUR haploid
daughter cells are produced
from ONE diploid parent cell.
 During
meiosis the cell actually
divides TWICE  Meiosis I
and Meiosis II
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of
DNA replication, forming
duplicate Chromosomes.
Each chromosome pairs with
its corresponding
homologous chromosome to
form a tetrad.
Spindle fibers attach to the
chromosomes.
The fibers pull the
homologous chromosomes
toward the opposite ends of
the cell.
Go to
Section:
MEIOSIS I
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a.
Prophase I:
Homologous chromosome pairs move together, to
form a tetrad. This pairing is called SYNAPSIS
b. Nuclear membrane disappears
c.
Crossing-over may occur at the CHIASMATA
Crossing over allows for the exchange of genetic
information between neighboring homologous
chromosomes
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of
DNA replication, forming
duplicate Chromosomes.
Each chromosome pairs with
its corresponding
homologous chromosome to
form a tetrad.
Spindle fibers attach to the
chromosomes.
The fibers pull the
homologous chromosomes
toward the opposite ends of
the cell.
Go to
Section:
Crossing-Over
Section 11-4
Go to
Section:
Crossing-Over
Section 11-4
Go to
Section:
Crossing-Over
Section 11-4
Go to
Section:
MEIOSIS I
 Metaphase
I:
a.
Tetrads line up at the
Equator.
b. Homologous Chromosomes
line up next to each other
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of
DNA replication, forming
duplicate Chromosomes.
Each chromosome pairs with
its corresponding
homologous chromosome to
form a tetrad.
Spindle fibers attach to the
chromosomes.
The fibers pull the
homologous chromosomes
toward the opposite ends of
the cell.
Go to
Section:
MEIOSIS I
 Anaphase
I:
a. ONE homologous chromosome
of each pair gets pulled to opposite
poles.
b. The sister chromatids do not
separate. It is still DIPLOID
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of
DNA replication, forming
duplicate Chromosomes.
Each chromosome pairs with
its corresponding
homologous chromosome to
form a tetrad.
Spindle fibers attach to the
chromosomes.
The fibers pull the
homologous chromosomes
toward the opposite ends of
the cell.
Go to
Section:
MEIOSIS I
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a.
b.
Telophase I and Cytokinesis:
Cells separate; two new cells are
formed that are HAPLOID.
Nuclear membrane REFORMS.
Interphase
Interphase occurs between
meiosis I and meiosis II to
prepare the cell for division
again
 NO DNA REPLICATION
HAPPENS!!
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Prophase II
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Chromosomes come together
Spindle fibers appear
Metaphase II
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The chromosomes align along middle of the
equator.
Anaphase II
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the fibers pull the chromatids apart and toward
opposite ends of the cells. Called disjunction
Telophase II
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The chromatids arrive at the either end of each
cell and new nuclear membranes form.
Cytokinesis
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The rest of the cell continues to divide. Only
when two, distinct cells form will cytokinesis,
the division of the cell's cytoplasm, be complete.
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Final Results of Meiosis
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4 haploid daughter cells which will develop into
sex cells
Each daughter cell has half of the genetic
information of a somatic cell
23 chromosomes for each sex cell
NOTE:
Males will create 4 sperm cells for every one cell that
goes through meiosis
Females will create 4 egg cells, BUT 3 will turn into
non usabale polar bodies and 1 will mature into an
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Meiosis Animation
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http://www.sumanasinc.com/webcontent/anim
ations/content/meiosis.html