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Cell DivisionMitosis & Meiosis
Yoga Dwi Jatmiko, S.Si., M.App.Sc
Basic Biology for Food Tech. Faculty
2012
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Mitosis
Eukaryotes divide by a more complicated system called Mitosis This is because:
1. They have a nucleus which must be broken up and thenreformed
2.They have their DNA packaged in the form ofChromosomes
3. Chromosomes are composed of ChromatinMade of DNA Strands & Proteins
4. Also contain Nucleosomes containing Histones Proteinsthe DNA is wrapped around Name for the DNA/Proteincomplex is Chromatin
5. They usually have more than 1 chromosome (Humans have23 pairs)
6. They have numerous organelles to equally share
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Chromatin / Chromosomes
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All chromosomes are duplicated
Do they contain identical genes?
That means: two copies of each chromosome
What are the copies called?
Sister chromatids
Yes, but
What about meiosis?
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Some terminology
Double-chromatid chromosomes
Single-chromatid chromosomes
Chromatin
Homologous chromosomes
Chromatid
When do each of these occur?
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The Cell Cycle
Most of the cell's life is spent doingits regular function.Cells divide along a rough time framecalled its Cell Cycle.The Cell cycle consists of the
folowing steps:G1 (Gap 1) Phase - Cell performs itsnormal function (cells which do notdivide stay in this stage for theirentire life span)S (Synthesis) Phase - Here the cell
actively duplicates its DNA inpreparation for divisionG2 (Gap 2) Phase - Amount ofcytoplasm (including organelles)increases in preparation for division.Mitosis - Actual division occurs
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Interphase
Cell Replicates its DNA/Chromosomesin preparation of upcoming division
Animal Cell Plant cell
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Prophase
1.Chromosomes Shortenand become visible.
2. Centrioles move toopposite sides of thecell
3. Nuclear envelopedisappears
4. Spindle Fibers & AstralFibers both togetherare known as theSpindle Apparatusbegin to form
Animal Cell
Plant Cell
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Metaphase
Chromosomes line upalong center of cellcalled the
Metaphase Plate Chromosomes attach
to spindle fibers
Spindle & Astralfibers are nowclearly visible
Animal Cell
Plant Cell
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Anaphase
Centromeres breakup separatingchromosome copies
Chromosomes arepulled apart toopposite sides of cell
Spindle & Astralfibers begin tobreak down
Animal Cell
Plant Cell
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Telophase (cytokenesis)
Nuclear envelope formsaround both sets ofchromosomes
DNA uncoils
Spindle & Astral fiberscompletely disappear Cytokenesis happens with
most (but not all) cells Cytoplasm & organelles
move (mostly equally) toeither side of the cell.CellMembrane pinches toform 2 separate cells
AnimalCell
PlantCell
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Plant and Animal cells dividedifferently
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Centrioles
Chromatin
Interphase
Nuclearenvelope
Cytokinesis
Nuclearenvelopereforming
Telophase
Anaphase
Individualchromosomes
Metaphase
Centriole
Spindle
CentrioleChromosomes
(paired chromatids)
Prophase
Centromere
Spindleforming
Interphase
G1 - Cell grows
S - DNA duplicates
G2 - Cell prepares for division
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Centrioles
Chromatin
Interphase
Nuclearenvelope
Cytokinesis
Nuclearenvelopereforming
Telophase
Anaphase
Individualchromosomes
Metaphase
Centriole
Spindle
CentrioleChromosomes
(paired chromatids)
Prophase
Centromere
Spindleforming
Mitosis - Prophase
1. DNA condenses to form chromosomes
2. Spindle forms
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Centrioles
Chromatin
Interphase
Nuclearenvelope
Cytokinesis
Nuclearenvelopereforming
Telophase
Anaphase
Individualchromosomes
Metaphase
Centriole
Spindle
CentrioleChromosomes
(paired chromatids)
Prophase
Centromere
Spindleforming
Mitosis - Metaphase
Chromosomes line up along the middle of the cell
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Centrioles
Chromatin
Interphase
Nuclearenvelope
Cytokinesis
Nuclearenvelopereforming
Telophase
Anaphase
Individualchromosomes
Metaphase
Centriole
Spindle
CentrioleChromosomes
(paired chromatids)
Prophase
Centromere
Spindleforming
Mitosis - Anaphase
Chromosomes separate and are pulled to
opposite sides of the cell
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Centrioles
Chromatin
Interphase
Nuclearenvelope
Cytokinesis
Nuclearenvelopereforming
Telophase
Anaphase
Individualchromosomes
Metaphase
Centriole
Spindle
CentrioleChromosomes
(paired chromatids)
Prophase
Centromere
Spindleforming
Mitosis - Telophase
1. Nuclear envelope forms
2. Cell contents are separated as the cells begin to
pinch apart
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Centrioles
Chromatin
Interphase
Nuclearenvelope
Cytokinesis
Nuclearenvelopereforming
Telophase
Anaphase
Individualchromosomes
Metaphase
Centriole
Spindle
CentrioleChromosomes
(paired chromatids)
Prophase
Centromere
Spindleforming
Cytokinesis
Cells pinch off to form two daughter cells each
genetically identical to the parent cell
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Putting it all together
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Mitosis Questions
1. What does diploid mean?
2. We have __ total chromosomes.
3. In the term 2n, what does n stand for inus?
4. Why does mitosis occur? Majorfunctions?
5. In what cells (general term) does mitosisoccur?
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Meiosis
A. Phases of Meiosis
1. Meiosis I2. Meiosis II
B. Comparing Mitosis and Meiosis
Go toSection:
M i i
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Meiosis
Chromosome replicate
2 Cell divisions occur(Meiosis I & MeiosisII)
4 daughter cells aremade all are (n):haploid
Homologous Chromsseparate in meiosis I
Meiosis II = Mitosis(chromatids separate)
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Meiosis
Gametes sex cells; egg and sperm Homologous Chromosomes - chromosomes in a cell that
pair during meiosis because they code for similargenes/features. For example, two chromosomes may
have genes encoding eye color, but one may code forbrown eyes (from mom), the other for blue (from dad). Diploid (2N) cells (somatic) that have two homologous
copies of each chromosome, usually one from themother and one from the father. (Humans = 46
chromosomes) Haploid (n) - the number of chromosomes in a gamete
of an individual. (Humans = 23 chromosomes)
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Interphase I Prophase I Metaphase I Anaphase I
Cells undergo a roundof DNA replication,
forming duplicateChromosomes.
Each chromosome pairswith its corresponding
homologous chromosometo form a tetrad.
Spindle fibers attach to thechromosomes.
The fibers pull thehomologous chromosomes
toward the opposite ends ofthe cell.
Go toSection:
Meiosis I
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Interphase I Prophase I Metaphase I Anaphase I
Cells undergo a roundof DNA replication,
forming duplicateChromosomes.
Each chromosome pairswith its corresponding
homologous chromosometo form a tetrad. Crossingover occurs.
Spindle fibers attach to thechromosomes.
The fibers pull thehomologous chromosomes
toward the opposite ends ofthe cell.
Go toSection:
Meiosis I
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Go toSection:
Crossing Over (Synapsis)
The chance that any two sex cells will be identical is 1 in 8,388,608!
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Crossing Over
During metaphase 1homologouschromosomes line-up
along the metaphaseplate
Areas of homologouschromosomes
connect at areascalled chiasmata
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Figure 8.18A
TetradChaisma
Centromere
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Crossing over contd.
Crossing Over of genesoccurs now Segments of homologous
chromosomes break and
reform at similarlocations.
Results in new geneticcombinations ofoffspring.
This is the mainadvantage of sexualreproduction
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Chromosome reduction
During anaphase 1,each homologouschromosome ispulled to opposite
sides of the cell.Unlike mitosis,THECENTROMERES
DO NOT BREAK.
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Interphase I Prophase I Metaphase I Anaphase I
Cells undergo a roundof DNA replication,
forming duplicateChromosomes.
Each chromosome pairswith its corresponding
homologous chromosometo form a tetrad.
Spindle fibers attach to thechromosomes.
The fibers pull thehomologous chromosomes
toward the opposite ends ofthe cell.
Go toSection:
Meiosis I
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Interphase I Prophase I Metaphase I Anaphase I
Cells undergo a roundof DNA replication,
forming duplicateChromosomes.
Each chromosome pairswith its corresponding
homologous chromosometo form a tetrad.
Spindle fibers attach to thechromosomes.
The fibers pull thehomologous chromosomes
toward the opposite ends ofthe cell.
Go toSection:
Meiosis I
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Meiosis I results in twohaploid (N) daughter cells,each with half the numberof chromosomes as theoriginal.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line upin a similar way to themetaphase stage of mitosis.
The sister chromatidsseparate and move towardopposite ends of the cell.
Meiosis II results in fourhaploid (N) daughter cells.
Go toSection:
Meiosis II
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Meiosis I results in twohaploid (N) daughter cells,each with half the numberof chromosomes as theoriginal.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line upin a similar way to themetaphase stage of mitosis.
The sister chromatidsseparate and move towardopposite ends of the cell.
Meiosis II results in fourhaploid (N) daughter cells.
Go toSection:
Meiosis II
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Meiosis I results in twohaploid (N) daughter cells,each with half the numberof chromosomes as theoriginal.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line upin a similar way to themetaphase stage of mitosis.
The sister chromatidsseparate and move towardopposite ends of the cell.
Meiosis II results in fourhaploid (N) daughter cells.
Go toSection:
Meiosis II
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Meiosis I results in twohaploid (N) daughter cells,each with half the numberof chromosomes as theoriginal.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line upin a similar way to themetaphase stage of mitosis.
The sister chromatidsseparate and move towardopposite ends of the cell.
Meiosis II results in fourhaploid (N) daughter cells.
Go toSection:
Meiosis II
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Meiosis I results in twohaploid (N) daughter cells,each with half the numberof chromosomes as theoriginal.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line upin a similar way to themetaphase stage of mitosis.
The sister chromatidsseparate and move towardopposite ends of the cell.
Meiosis II results in fourhaploid (N) daughter cells.
Go toSection:
Meiosis II
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Meiosis Summary
2. Meiosis 2a. There is no more DNA replication
b. The chromatids of each chromosome
separate and each daughter cell dividesc. At the end of Meiosis 2, there are 4daughter cells from each parent cell. Eachdaughter cell has half the number of
chromosomes as the parent cell
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1. The cells produced in meiosis are_____ (haploid or diploid?)
2. Sex cells are called ________.
_____ are produced by males, ____by females.
3. Whats crossing over and why is itimportant?
Meiosis Questions
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4. In what meiotic stage does crossingover occur?
5. Why are sex cells n, not 2n?
6. If a species diploid number is 50,what is n?
Meiosis Questions
Diff B t Mit i d M i i
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Differences Between Mitosis and MeiosisMitosis Meiosis
Interphase
chromosomesduplicate
Interphase I
chromosomesduplicate
Prophase homologous
chromosomes do not cross over
Prophase I homologous
chromosomes do cross over
Metaphase chromosomes all
lined up in a single row
Metaphase I chromosomes all
lined up in a double row
Anaphase chromatids
separate
Anaphase I chromatids do not
separate
Telophase homologous
chromosomes not separated
Telophase I homologous
chromosomes separate
Each daughter cell has the same
number of chromosomes as the
original cell (diploid, 2n)
PMAT repeats.
Each daughter cell has half the
number of chromosomes as the
original cell (haploid, n) and is
genetically unique
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Figure 8.15
MITOSIS MEIOSIS
PARENT CELL(before chromosome replication)
Site ofcrossing over
MEIOSIS I
PROPHASE ITetrad formed
by synapsis ofhomologouschromosomes
PROPHASE
Duplicatedchromosome(two sister chromatids)
METAPHASE
Chromosomereplication
Chromosomereplication
2n= 4
ANAPHASETELOPHASE
Chromosomesalign at themetaphase plate
Tetradsalign at themetaphase plate
METAPHASE I
ANAPHASE ITELOPHASE I
Sister chromatidsseparate duringanaphase
Homologouschromosomesseparateduringanaphase I;sisterchromatids
remain together
No furtherchromosomalreplication; sisterchromatidsseparate duringanaphase II
2n 2n
Daughter cellsof mitosis
Daughter cells of meiosis II
MEIOSIS II
Daughter
cells ofmeiosis I
Haploidn= 2
n n n n
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Bacteria andBinary Fission
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Thank you
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