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Cell Reproduction
Chapters 10 & 11
OCC BIO-114
Dave Werner
Video/Animation
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Eukaryotic Cell Reproduction
Mitosis set to Music
Mitosis Animation
Chromosomes
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During cell division, the DNA in a eukaryotic cell’s
nucleus is coiled tightly into Chromosomes
Each Chromosome is a single DNA molecule
associated with proteins
DNA molecule
Chromosome
Histones and Nonhistones
Histones are proteins
that the DNA wrap
around, and help
maintain the shape of
the chromosome
 Nonhistones are
proteins that are
involved in controlling
activity of the DNA
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Chromosomes
fig.10.5/10.7
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Each chromosome is made
up of 2 identical
chromatids
The chromatids are held
together by the centromere
In humans, we have 23 pairs
of chromosomes
 Or 46 chromosomes
 Or 92 chromatids
REMEMBER…..
 The
number of chromosomes that a
species has does NOT reflect on how
complex that animal may or may not be!!!
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Mosquito 3
Garden onion 8
Frog 13
House mouse 20
Human 23
Cattle 30
Horse 32
Carp 52
Pairs of chromosomes
Housefly 6
Rice12
Cat19
Wheat 21
Potato 24
Donkey 31
Dog 39
Chromosomes
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Human and animal chromosomes are categorized
as either sex chromosomes or autosomes
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What name do we give the sex chromosomes of
humans?
 Hint: 2 letters
X & Y
Sex chromosomes
fig.10.6
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These chromosomes
determine the sex of an
organism, and may carry
genes for other
characteristics
Only 1 pair of
chromosomes are
considered sex
chromosomes, while the
other 22 pairs are
autosomes
Autosomes

Each cell contains 2 copies of each autosome.
In other words, an autosome is a chromosome, so there
are 2 identical chromosomes, for each of the 22
autosomes
 Chromosomes are made up of 2 identical chromatids.
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Therefore, how many chromatids are found in each pair of
autosomes?
Autosomes
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The two copies of each
autosome are called
homologous
chromosomes or
homologues because
there are the same size,
shape, and carry the same
genes for specific
traits…EVEN though
they come from two
separate parents!
Fruit Fly
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The Fruit Fly contains 8 chromosomes
How many of those 8 are sex chromosomes?
2
How many of those 8 are autosomes?
6
How many homologous pairs are present?
4
If each chromosome is made up of 2 chromatids, how
many chromatids does this fly have in EACH cell?
16
Karyotype
fig.10.6
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A Karyotype is a photomicrograph of all the
chromosomes found in a cell that are paired up
into homologues based on their size and shape
Diploid (2n) cells
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Cells having 2 sets of chromosomes are
considered to be diploid or 2n.
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Every cell in the human body EXCEPT
reproductive cells (sperm and egg cells) are diploid
or 2n
Haploid 1n cells
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Sperm and egg cells are haploid or 1n cells.
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When the haploid 1n sperm and the haploid 1n
egg cells join together, what do they form?
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Why do the sex cells only contain 1 set of
chromosomes rather than 2?
Cell Division
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Binary Fission is the division of prokaryotic
cells into identical cells
The chromosome makes a copy of itself
 The cell continues to grow until it is doubled in size
 A Cell wall forms between the 2 chromosomes
 The cell splits into 2 new cells
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Binary Fission
STAGE 1 - The Chromosome, which is
attached to the Inside of the Cell
Membrane, makes a COPY of Itself,
Resulting in Two Identical Chromosomes
Attached to the Inside of the Inner Cell
Membrane.
STAGE 2 - The Cell continues to grow
until it reaches approximately TWICE its
Normal Size. Then a CELL WALL
Begins forms between the Two
Chromosomes.
STAGE 3 - The Cell SPLITS into TWO
NEW CELLS. Each New Cell contains
on the Identical Chromosomes
Cell Division
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Mitosis results in new cells with genetic material
that is identical to that of the original cell
Cell Cycle
fig.10.8
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Cell cycle is the
repeating set of
events that make up
the life of a cell, with
cell division making
up only one phase
Cell Cycle
Interphase – Majority of the cell lifetime
G1 Phase
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1.
Cells grow to a mature size
2.
S Phase
DNA within the cell is copied
3.
G2 Phase
Cell prepares for cell division
Cell Cycle
Mitosis or M Phase
Division of the Nucleus
Mitosis
fig.10.11
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1. Prophase
 DNA is tightly coiled into chromosomes, which is
made up of 2 chromatids held together by the
centromere
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Remember that the chromosomes were copied during the S
Phase of Interphase
Nucleolus and Nuclear membrane break down and
disappear
 Two pairs of centrosomes appear each made up of 2
centrioles
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Plant cells do not contain centrioles
Mitosis
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1. Prophase (Continued)
Centrosomes move toward opposite poles of the cell
 Spindle fibers made up of microtubules radiate from
the centrosomes which make up the mitotic spindle
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Spindle Fibers
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1. Kinetochore fibers attached to a protein called
kinetochore found in the centromere region
 These fibers extend from the chromatid to the
kinetochore
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2. Polar Fibers extend from one centrosome to
the other
Mitosis
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2. Metaphase
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Kinetochore fibers move the choromosomes to the
center of the cell, and then hold them in place
Mitosis
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3. Anaphase
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Chromatids of each chromosome separate at the
centromere and slowly move toward opposite poles
of the cell
Mitosis
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4. Telophase
Spindle fibers disassemble and the chromosomes
begin to uncoil
 Nuclear envelope and Nucleolus form
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Cytokinesis
Cytoplasm of the cell divides
 Cell membrane “Pinches off” and
separates into 2 cells
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In plants, rather than pinching off, since
cell walls are so hard, a cell plate is formed
by the Golgi apparatus
fig.10.14
Mitosis
BioClip – Mitosis Animation
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http://www.loci.wisc.edu/outreach/bioclips/C
DBio.html
Tumors & Cancer
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Tumor = cells dividing at
an abnormally high rate.
Neoplasms = Moles &
other tumors
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Benign Tumors = Not
harmful
Malignant Tumors =
Cancer
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Metastasis – rapid growth
& spreading
Meiosis – Ch.11
MeiosisVideo
Meiosis
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While Mitosis is the division of body cells into exact
copies, meiosis is the division of cells twice to form sex
cells (Sperm and Egg)
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EGGS are larger than sperm and contain a lot of
Cytoplasm. An egg is nonmotile.
SPERM Cells contain very little Cytoplasm, have
Flagella, that helps them swim to the nonmotile egg
The Chromosomes of Two Gametes are added
together when they join.
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Meiosis
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Cells that undergo Meiosis divide twice.
The first cell division is known as Meiosis I
 The second cell division is known as Meiosis II
 Rather than one cell forming two diploid cells (2n),
like in mitosis, the cells form 4 haploid (1n) cells in
meiosis.
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Meiosis I
Prophase I
DNA coils tightly into chromosomes
Spindle fibers appear
Nucleus and Nucleolus disappear
Chromosomes line up with its homologue
Synapsis is the pairing of homologous
chromosomes
Meiosis I
Prophase I
Tetrad is the pair of homologous chromosomes
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Tetrad = 4 because there are 4 chromatids for each
homologous pair… like a tetrapod! During synapsis,
chromatids within a homologous pair twist around
one another
Meiosis I (fig.11.8)
Prophase I
Portions of Chromatids
may Break Off and
attach to Adjacent
Chromatids on the
homologous
Chromosome - a
process called
CROSSING-OVER
Crossing Over results
in genetic
recombination
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Meiosis I
Metaphase I
Tetrads line up along the mid-line of the
dividing cell (think meta – middle)
Spindle fibers from each pole attach to the
centromeres of each of the homologues
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Meiosis I
Anaphase I
Each homologous chromosome moves to
opposite poles of the dividing cells
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The separation of the homologous
chromosomes is known as independent
assortment, which is another way for genetic
variation
Meiosis I
Telophase I
Chromosomes reach opposite ends of the cell,
and cytokinesis begins
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Meiosis I (fig.11.8)
Meiosis II
Prophase II
Spindle fibers form and begin to move the chromosomes toward
the midline of the dividing cell
 Metaphase II
Chromosomes move to the midline of the dividing cell facing
opposite poles
 Anaphase II
Chromatids separate and move toward opposite poles of the cell
 Telophase II
Nuclear membrane forms around the chromosomes in each of the
4 new cells which contain HALF of the original cell’s # of
chromosomes = 4 Haploid offspring cells.
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Meiosis II (fig.11.7/11.8)
Meiosis
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Meiosis occurs in only the reproductive organs
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In humans, meiosis occurs in the testes and
ovaries
Formation of Gametes
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In the testes, meiosis produces sperms cells or
spermatozoa.
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A diploid (2n) reproductive cell divides meiotically to form 4
haploid (1n) cells called spermatids
The production of sperm cells is called spermatogenesis
In the ovaries, meiosis produces egg cells or ova
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A diploid (2n) reproductive cell divides meiotically to form 1
haploid (1n) cell called ovum, and 3 haploid (1n) polar
bodies which eventually degenrate
The production of and egg cell is called oogenesis
Spermatogenesis (fig.11.3)
Oogenesis (fig.11.3)
Asexual Reproduction
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Asexual reproduction is the production of
offspring from one parent.
Usually does not involve meiosis or gametes.
 Most commonly by binary fission or mitosis
 Offspring is identical to parent
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Sexual Reproduction
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Sexual Reproduction is the production of
offspring through meiosis and the union of a
sperm and an egg.
Offspring produced are genetically different from
parents
 Allows for genetic variation
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Comparing Mitosis to Meiosis
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NOVA Online = good study tool
Can you identify the differences/Similarities???