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QOD
How many chromosomes do
you have? Identify them.
How many from your
father? Mother?
Chapter 8: Cell
Reproduction
Section 8-1:
Chromosomes
Chromosome
Structure
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Chromosome Structure
 Chromosomes
= DNA + Proteins
 Levels of organization:
– DNA
– Nucleosome = DNA + Histones
– Coils
– Supercoils
– Chromosome
Chapter 8
Section 1 Chromosomes
Chromosome Structure
Chromosome
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Chromosomes
 Before
Cell Division
– Chromatin
– Thinned out
 During
Cell Division
– Thickened
– Chromosomes
 Chromatids
 Centromere
(2)
Chromosome Types and Numbers
 Types:
– Sex chromosomes
– Autosomes
– Homologous chromosomes
– Karyotype
 Numbers:
– Diploid (2n)
– Haploid (n)
Karyotype
Karyotype
QOD
How many chromosomes
does a skin cells have after
it divides by mitosis? What
happens to ensure this
number is achieved?
When?
Chapter 8: Cell
Reproduction
Section 8-2: Cell Division
Cell Division
 In
Prokaryotes
– Binary fission
 In
Eukaryotes
– Mitosis
– Meoisis
Chapter 8
Section 2 Cell Division
Cell Division in Prokaryotes
QOD
Define mitosis. What is the
end result of mitosis?
Stages of
Cell Cycle
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III. The Cell Cycle
 Interphase
– G1
–S
– G2
M
Phase
– Mitosis
– Cytokinesis
The M phase
 Mitosis
– Division of the nucleus
– Prophase
– Metaphase
– Anaphase
– Telophase
 Cytokinesis
cytoplasm
– Division of the
Mitosis
Animal cell
undergoing
mitosis
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Prophase
 Nucleus
disappears
 Centrosomes/Centrioles move
 Spindle fibers form – mitotic spindle
– Kinetochore fibers/ Kinetochore
– Polar fibers
Mitosis continues
 Metaphase
– Metaphase plate
 Anaphase
– Role of kinetochore
 Telophase
– Reversal of prophase
– Results:
QOD
How does the cell control
the cell cycle? What
happens when control is
lost?
Animal cell
undergoing
mitosis
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Plant Cell Undergoing Mitosis
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Cytokinesis
 Division
of the cytoplasm
 Separates two nuclei into two distinct
daughter cells
 Animal cells – cleavage
 Plant cells – form cell plate
Control of Cell Division
 Checkpoints:
– G1
– G2
– Mitosis
 Loss
of control
– Cancer
QOD
Compare and contrast
mitosis to meiosis
Chapter 8: Cell
Reproduction
Section 8-3: Meiosis
Homologous
Chromosome
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Meiosis
 “Reduction”
division
 Produces gametes
 2 divisions
 Diploid  haploid
 Fertilaztion – n + n = 2n
Meiosis
Diagram
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Meiosis I
 Prophase
I
– Much of it same as prophase in mitosis
 Nucleus/nucleolus
disappears
 Chromosomes
coil
 Centrioles and spindle fibers
– Homologous chromosomes pair up
 Synapsis
 Forms
a tetrad
 Crossing-over  genetic recombination
Crossing Over Diagram
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QOD
What is independent
assortment?
Meiosis I
 Metaphase
I
– Tetrads line up
 Anaphase
I
– Independent assortment  genetic
variation
 Telophase
I
– Cytokinesis begins
– Forms 2 haploid cells
LE 13-8ab
MEIOSIS I: Separates homologous chromosomes
METAPHASE I
PROPHASE I
ANAPHASE I
Sister chromatids
remain attached
Centromere
(with kinetochore)
Sister
chromatids
Chiasmata
Metaphase
plate
Spindle
Tetrad
Homologous chromosomes
(red and blue) pair and
exchange segments; 2n = 6
in this example
Microtubule
attached to
kinetochore
Tetrads line up
Homologous
chromosomes
separate
Pairs of homologous
chromosomes split up
Meiosis II
 No
copying of DNA
 Follows process of mitosis
 Prophase II
 Metaphase II
 Anaphase II
 Telophase II
 Cytokinesis
LE 13-8b
MEIOSIS II: Separates sister chromatids
TELOPHASE I AND
CYTOKINESIS
PROPHASE II
Cleavage
furrow
Two haploid cells
form; chromosomes
are still double
METAPHASE II
ANAPHASE II
Sister chromatids
separate
TELOPHASE II AND
CYTOKINESIS
Haploid daughter cells
forming
During another round of cell division, the sister chromatids finally separate;
four haploid daughter cells result, containing single chromosomes
Results
 Gametes
– 4 haploid cells
– Genetically different
 Males:
– Spermatogensis
 Females:
– Oogenesis
– 1 egg cell, 3 polar bodies
Chapter 8
Section 3 Meiosis
Meiosis in Male and Female
Animals