Cell Growth
and Division
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1
Cell Cycle
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2
Keeping Cells
Identical
The instructions for
making cell parts
are encoded in the
DNA, so each new
cell must get a
complete set of the
DNA molecules
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3
DNA Replication
✓DNA must be
Original DNA
copied or
strand
replicated
before cell
division
Two new,
identical DNA
✓Each new cell
strands
will then have an
identical copy of
the DNA
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4
Identical Daughter Cells
Two
identical
daughter
cells
Parent Cell
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5
Chromosomes
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6
Prokaryotic Chromosome
✓The DNA of
prokaryotes
(bacteria) is one,
circular
chromosome
attached to the
inside of the cell
membrane
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7
Eukaryotic
Chromosomes
✓All eukaryotic cells store
genetic information in
chromosomes
✓Most eukaryotes have between
10 and 50 chromosomes in
their body cells
✓Human body cells have 46
chromosomes or 23 identical
pairs
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8
Eukaryotic Chromosomes
✓Each chromosome is composed of a
single, tightly coiled DNA molecule
✓Chromosomes can’t be seen when
cells aren’t dividing and are called
chromatin
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9
Compacting DNA into
Chromosomes
✓DNA is
tightly
coiled
around
proteins
called
histones
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10
Chromosomes in Dividing Cells
✓Duplicated
chromosomes are
called
chromatids &
are held
together by the
centromere
Called Sister Chromatids
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11
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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12
Boy or Girl?
The Y Chromosome Decides
Y - Chromosome
X - Chromosome
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13
The Cell
Cycle
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14
Cell Cycle
DNA Copied
Cells prepare for
Division
Cells
Mature
Daughter
Cells
Cell Divides into
Identical cells
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15
Five Phases of the Cell
Cycle
✓G1 - primary growth phase
✓S – synthesis; DNA replicated
✓G2 - secondary growth phase
collectively the 3 stages above
are called interphase
✓M - mitosis
✓C - cytokinesis
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16
Interphase - G1
Stage
✓1st growth stage after cell
division
✓Cells mature by making more
cytoplasm & organelles
✓Cell carries on its normal
metabolic activities
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17
Interphase – S
Stage
✓Synthesis stage
✓DNA is copied or
replicated
Two
identical
copies
of DNA
Original
DNA
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18
Interphase – G2
Stage
✓2nd Growth Stage
✓Occurs after DNA has been copied
✓All cell structures needed for
division are made (e.g. centrioles)
✓Both organelles & proteins are
synthesized
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19
What’s Happening in Interphase?
What the cell looks like
Animal Cell
What’s occurring
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20
Mitosis
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21
Mitosis
✓Division of the
nucleus
✓Also called
karyokinesis
✓Only occurs in
eukaryotes
✓Has four stages
✓Doesn’t occur in
some cells such
as brain cells
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22
Four Mitotic Stages
✓Prophase
✓Metaphase
✓Anaphase
✓Telophase
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23
Early Prophase
✓Chromatin in nucleus condenses to form
visible chromosomes
✓Mitotic spindle forms from fibers in
cytoskeleton or centrioles (animal)
Cytoplasm
Nucleolus
Nuclear Membrane
Chromosomes
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24
Late Prophase
✓Nuclear membrane & nucleolus are
broken down
✓Chromosomes continue condensing & are
clearly visible
✓Spindle fibers called kinetochores
attach to the centromere of each
chromosome
✓Spindle finishes forming between the
poles of the cell
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25
Late Prophase
Chromosomes
Nucleus & Nucleolus have disintegrated
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26
Spindle Fiber attached to
Chromosome
Kinetochore Fiber
Chromosome
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27
Review of Prophase
What the cell
looks like
What’s
occurring?
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28
Spindle Fibers
✓ The mitotic spindle form from the
microtubules in plants and centrioles in
animal cells
✓ Polar fibers extend from one pole of
the cell to the opposite pole
✓ Kinetochore fibers extend from the
pole to the centromere of the
chromosome to which they attach
✓ Asters are short fibers radiating from
centrioles
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29
The Spindle
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30
Metaphase
✓Chromosomes, attached to the
kinetochore fibers, 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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31
Metaphase
Asters at
the poles
Spindle
Fibers
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Chromosomes
lined at the
Equator
32
Metaphase
Aster
Chromosomes at Equator
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33
Review of Metaphase
What the cell looks
like
What’s
occurring
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34
Anaphase
✓Occurs rapidly
✓Sister
chromatids are
pulled apart to
opposite poles
of the cell by
kinetochore
fibers
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35
Anaphase
Sister
Chromatids
being
separated
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36
Anaphase Review
What the
cell looks
like
What’s
occurring
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37
Telophase
✓Sister chromatids at opposite poles
✓Spindle disassembles
✓Nuclear envelope forms around each
set of sister chromatids
✓Nucleolus reappears
✓CYTOKINESIS occurs
✓Chromosomes reappear as chromatin
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38
Comparison of Anaphase & Telophase
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39
Cytokinesis
✓Means division of the cytoplasm
✓Division of cell into two,
identical halves called daughter
cells
✓In plant cells, cell plate forms
at the equator to divide cell
✓In animal cells, cleavage furrow
forms to split cell
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40
Cytokinesis
Cleavage furrow
in animal cell
Cell plate in
plant cell
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41
Mitotic Stages
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42
Daughter Cells of
Mitosis
✓Have the same number of
chromosomes as each other and as
the parent cell from which they
were formed
✓Identical to each other, but smaller
than parent cell
✓Must grow in size to become mature
cells (G1 of Interphase)
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43
Identical Daughter
Cells
What is
the 2n
or
diploid
number?
2
Chromosome number the same, but cells
smaller than parent cell
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44
Review
of
Mitosis
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45
Draw & Learn these Stages
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46
Draw & Learn these Stages
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47
Name the Mitotic Stages:
Name this?
Name this?
Name this?
Name this?
Name this?
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48
Name the Mitotic Stages:
Interphase
Prophase
Telophase
Metaphase
Anaphase
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49
Eukaryotic Cell Division
✓ Used for growth and repair
✓ Produce two new cells
identical to the original cell
✓ Cells are diploid (2n)
Chromosomes during
Metaphase of mitosis
Prophase
Metaphase
Anaphase Telophase Cytokinesis
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50
Mitosis in Onion Root Tips
Do you see any stages of mitosis?
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51
Test Yourself
over Mitosis
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52
Mitosis Quiz
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53
Mitosis Quiz
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54
Name the Stages of Mitosis:
1.
2
4.
3.
6.
5.
7.
8.
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9.
55
Name the Stages of Mitosis:
3. Early
prophase
1. Early Anaphase
5. Early
4. Metaphase Telophase,
Begin
cytokinesis
2. Interphase
8. Mid-Prophase
6. Late
Prophase
7. Late telophase,
Advanced
cytokinesis
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9. Late
Anaphase
56
Identify? the Stages
?
?
?
?
(h
)
(i)
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?
?
(j)
57
Identify? the Stages
Early, Middle, & Late Prophase
?
?
Metaphase
Late Prophase
Late Anaphase
Anaphase
?
?
Telophase
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?
?
Telophase &
Cytokinesis
58
Locate the Four Mitotic
Stages in Plants
C)
D)
B)
A)
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59
Locate the Four Mitotic
Stages in Plants
C) Anaphase
D) Telophase
B) Metaphase
A) Prophase
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60
Uncontrolled Mitosis
✓ If mitosis is not
controlled, unlimited
cell division occurs
causing cancerous
tumors
✓ Oncogenes are special
proteins that increase
the chance that a
normal cell develops
into a tumor cell
Lung Cancer Cells
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61
What’s wrong with cancer cells?
Image Credit and Learn More about the Cell Cycle and
62
Cell Division in
Prokaryotes
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63
Cell Reproduction
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64
Types of Cell Reproduction
✓Asexual reproduction involves a single
cell dividing to make 2 new, identical
daughter cells
✓Mitosis & binary fission are examples
of asexual reproduction
✓Sexual reproduction involves two cells
(egg & sperm) joining to make a new
cell (zygote) that is NOT identical to
the original cells
✓Meiosis is an example
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65
Asexual Reproduction by Binary
Fission
Sketch the “Visual Vocab”
diagram on p. 148
✓ Prokaryotes such as
Parent
bacteria divide into 2
cell
identical cells by the
process of binary
Chromosome
fission
replicates
✓ Single chromosome
makes a copy of
itself
Cell splits
✓ Cell wall forms
between the
chromosomes dividing
the cell
2 identical daughter cells
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66
Prokaryotic Cell Undergoing
Binary Fission
(similar to mitosis)
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67
Asexual Reproduction occurs in
Prokaryotes & some Eukaryotes
1) Binary Fission
2) Types of Asexual Reproduction 1
3) Types of Asexual Reproduction 2
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68
Some eukaryotes reproduce asexually 69
through mitosis:
70
Multicellular Life
● Tissues are groups of
cells that work
together to perform
a similar function.
● Organs are groups of
tissues that work
together to perform
a specific function or
related functions.
● Organ Systems are
groups of organs that
carry out similar
functions.
71
72
Specialized Cells Perform Specific
Functions: You began as a single fertilized egg.
73
74
75
76
Adult Stem Cells (Somatic Stem Cells)
-undifferentiated cells found all over the body among
specialized cells
Advantages:
-Can be taken
from a patient,
grown in
culture, and put
back into the
patient, avoiding
transplant
rejection.
-Avoid ethical
issues.
Disadvantages:
-few in number
-difficult to
isolate
-sometimes
tricky to grow
-may also
contain more
DNA
abnormalities
Adult Stem Cells treated with the right combination of molecules
may give rise to a completely different type of tissue. This is called
transdifferentiation, which remains an active area of research.
77
Embryonic Stem Cells
-most come from donated embryos grown in a clinic.
-an embryo is a fertilized egg
78
Meiosis
Formation of Gametes
(Eggs & Sperm)
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79
About Meiosis
✓Preceded by interphase which
includes chromosome replication
✓Two meiotic divisions --- Meiosis
I and Meiosis II
✓Called Reduction- division
✓Original cell is diploid (2n)
✓Four daughter cells produced that
are monoploid (1n)
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80
About Meiosis
✓Daughter cells contain half the
number of chromosomes as the
original cell
✓Produces gametes (eggs & sperm)
✓Occurs in the testes in males
(Spermatogenesis)
✓Occurs in the ovaries in females
(Oogenesis)
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81
About Meiosis
✓ Start with 46 double stranded
chromosomes (2n)
✓After 1 division - 23 double
stranded chromosomes (n)
✓After 2nd division - 23 single
stranded chromosomes (n)
✓ Occurs in our germ cells that
produce gametes
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82
Why Do we Need Meiosis?
✓It is the fundamental basis of
sexual reproduction
✓Two haploid (1n) gametes are
brought together through
fertilization to form a diploid (2n)
zygote
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83
Fertilization – “Putting it all
together”
2n = 6
1n =3
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84
Replication of Chromosomes
✓Replication is the
process of
duplicating a
chromosome
✓Occurs prior to Occurs in
Interphase
division
✓Replicated copies
are called sister
chromatids
✓Held together at
centromere
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85
A Replicated Chromosome
Gene X
Sister
Chromatids
Homologs
(same genes,
different alleles)
(same genes,
same alleles)
Homologs separate in meiosis I and
therefore different alleles separate.
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86
Meiosis Forms Haploid Gametes
✓ Meiosis must reduce the chromosome number
by half
✓ Fertilization then restores the 2n number
from
mom
from
dad
child
too
much!
meiosis reduces
genetic content
The right
number!
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87
Meiosis: Two Part Cell
Division Sister
chromatids
separate
Homologs
separate
Meiosis
I
Meiosis
II
Diploid
Diploid
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Haploid
88
Meiosis I: Reduction Division
Spindle
fibers
Nucleus
Early
Prophase I
(Chromosome
number
doubled)
Late
Prophase
I
Nuclear
envelope
Metaphase
Anaphase Telophase I
I
I
(diploid)
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89
Prophase I
Early prophase
✓Homologs pair.
✓Crossing over
occurs.
Late prophase
✓Chromosomes condense.
✓Spindle forms.
✓Nuclear envelope
fragments.
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90
Tetrads Form in
Prophase I
Homologous chromosomes
(each with sister
chromatids)
Join to form a
TETRAD
Called Synapsis
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91
Crossing-Over
✓ Homologous
chromosomes in
a tetrad cross
over each other
✓ Pieces of
chromosomes or
genes are
exchanged
✓ Produces
Genetic
recombination in
the offspring
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92
Homologous Chromosomes
During Crossing-Over
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93
Crossing-Over
Crossing-over multiplies the already huge
number of different gamete types
produced by independent assortment
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94
Metaphase I
Homologous pairs
of chromosomes
align along the
equator of the
cell
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95
Anaphase I
Homologs separate and
move to opposite poles.
Sister chromatids remain
attached at their
centromeres.
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96
Telophase I
Nuclear envelopes
reassemble.
Spindle disappears.
Cytokinesis divides cell
into two.
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97
Meiosis II
Gene X
Only one homolog of each
chromosome is present in
the cell.
Sister chromatids carry
identical genetic
information.
Meiosis II produces gametes with
one copy of each chromosome and
thus one copy of each gene.
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98
Meiosis II: Reducing
Chromosome Number
Prophase
II
Metaphase
Telophase
II
Anaphase
4 Genetically
II
Different
II
haploid cells
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99
Prophase II
Nuclear envelope
fragments.
Spindle forms.
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100
Metaphase II
Chromosomes align
along equator of
cell.
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101
Anaphase II
Equator
Pole
Sister chromatids
separate and
move to opposite
poles.
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102
Telophase II
Nuclear envelope
assembles.
Chromosomes
decondense.
Spindle disappears.
Cytokinesis divides
cell into two.
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103
Results of Meiosis
Gametes (egg & sperm)
form
Four haploid cells with
one copy of each
chromosome
One allele of each gene
Different combinations
of alleles for different
genes along the
chromosome
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104
Gametogenesis
Oogenesis
or
Spermatogenesis
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105
Spermatogenesis
✓Occurs in the
testes
✓Two divisions
produce 4
spermatids
✓Spermatids mature
into sperm
✓Men produce about
250,000,000
sperm per day
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106
Spermatogenesis in the
Testes
Spermatid
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107
Spermatogenesis
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108
Oogenesis
✓Occurs in the ovaries
✓Two divisions produce 3 polar bodies that
die and 1 egg
✓Polar bodies die because of unequal
division of cytoplasm
✓Immature egg called oocyte
✓Starting at puberty, one oocyte matures
into an ovum (egg) every 28 days.
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109
Oogenesis in the Ovaries
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110
Oogenesis
First polar body
may divide
(haploid)
a
Mitosis
Oogonium
(diploid)
X
A
X
X
a
X
a
a
Polar
bodies
die
X
Primary
oocyte
(diploid)
Meiosis I Meiosis II
(if fertilization
A
occurs)
X
A
X
Secondary
oocyte
(haploid)
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Ovum (egg) Mature
egg
A
X
Second
polar body
(haploid)
111
Comparing
Mitosis and
Meiosis
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112
Comparison of Divisions
Mitosis
Number of
divisions
Number of
daughter cells
Genetically
identical?
1
Meiosis
2
2
4
Yes
No
Same as parent
Half of parent
Where
Somatic cells
Germ cells
When
Throughout life
At sexual maturity
Chromosome #
Role
Growth and repair Sexual reproduction
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113
Thank You!

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114