Outline – Cell Reproduction
Examples of Cell Numbers
1. Overview of Cell Reproduction
Human Body Æ 50,000,000,000,000 cells
2. Cell Reproduction in Prokaryotes
Red blood cells Æ 25,000,000,000
3. Cell Reproduction in Eukaryotes
1. Chromosomes
2. Cell Cycle
3. Mitosis and Cytokinesis
RBCs replaced every day Æ 1,400,000,000
Intestinal Epithelium Cells Æ Last 1.5 days
4. Sexual Life Cycle & Meiosis
Figure 8.3A
Why do cells reproduce?
Binary fission of a prokaryotic cell
Plasma
membrane
Prokaryotic
chromosome
1. Single celled organisms – reproduction
Cell wall
1
Duplication of chromosome
and separation of copies
2
Cell elongation and
movement of DNA copies
Protein Ring
2. Multicellular organisms
1. Growth – increase number of cells
2. Maintenance of existing cells
3. Repair of damaged cells
3 Division into
two daughter cells
3
Genome Size Varies
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Eukaryote Chromosome Structure
Chromatids
Centromere
Chromatids
DNA
Histone
Protein
Centromere
1
Chromosome Structure
Karyotype of Human Chromosomes
Chromosome
Chromosome
Replication
Cell Cycle of Eukaryotes
Chromosome Numbers
INTERPHASE
G1
s
si
S - DNA Synthesis
G2
ito
si
s
e
in
M
C
ok
yt
INTERPHASE
G1 - Primary Growth
S
Reproductive Phase
M – Chromosomes condense and
chromatids separate
G2 – Mitochondria
replicate
Chromosomes
condense
C –Cytoplasm separates
Cytokinesis
Figure 8.6
Mitosis in Eukaryotes
The stages of cell division (part 1)
Stages of Mitosis
Prophase
LM
250×
Mitosis – Separation of Chromosomes
“Division” of Nucleus
INTERPHASE
Centrosomes
Metaphase
Chromatin
PROPHASE
PROMETAPHASE
Mitotic Centrosome Nuclear
Envelope Fragments
spindle
Kinetochore
Anaphase
Telophase
Nucleus
Plasma
membrane
Chromatids
Centromere
Spindle
Microtubules
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2
Figure 8.6
The stages of cell division (part 2)
Figure 8.7A
Cytokinesis in an animal cell
Cleavage
furrow
SEM 140×
TELOPHASE
ANAPHASE
METAPHASE
Cleavage furrow
Contracting ring of
microfilaments
Spindle
Chromatids
Separating
Metaphase
plate
Nuclear envelope
forming
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Figure 8.7B
Daughter cells
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Cell plate formation in a plant cell
Cell plate
Mitosis in Plant Cells
TEM 7,500×
Daughter
nucleus
Cell wall
Vesicles containing
cell wall material
New cell wall
Cell plate
Daughter cells
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Controlling the Cell Cycle
G1 checkpoint
G0
Control
system
G1
M
M checkpoint
Controlling the Cell Cycle
S
G2
G2 checkpoint
Figure 8.9A
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3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Controlling the Cell Cycle
PROTO-ONCOGENES
Growth factor receptor:
more per cell in many
breast cancers.
Growth factor
Plasma membrane
Cyclins & CyclinDependent
Relay
Kinases
proteins
G1 checkpoint
Receptor
protein
Signal
transduction
pathway
Control
system
G1
M
S
activated by mutations
in 20–30% of all cancers.
Src
kinase
Cytoplasm
Src kinase:
activated by mutations
in 2–5% of all cancers.
Rb
protein
Nucleus
TUMOR-SUPPRESSOR GENES
p53
protein
Cyclins & CyclinDependent Kinases
G2
Ras protein:
Ras
Signal
protein
transduction
pathway
Rb protein:
mutated in 40% of all
cancers.
p53 protein:
Cell cycle
checkpoints
mutated in 50% of all
cancers.
Figure 8.9B
20
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Interfering with Cell Division
Tumors
Radiation
Chemotherapy
Lymph
vessels
Tumor
Single
cancer
cell.
Blood
vessel
Invade
Neighboring
Tissue
Metastasize
Periwinkle - Vinblastin
Pacific Yew - Taxol
Figure 8.10
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Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
END
ENDMitosis
Mitosis
Meiosis
4
Unnumbered Figure p.149
Meiosis – Learning Goals
Haploid gametes (n = 23)
1.
2.
Understand the differences between homologous chromosomes
and sister chromatids.
Distinguish between
1. autosomes and sex chromosomes.
2. between somatic cells and reproductive cells
3. diploid cells and haploid cells.
n
n
Sperm cell
Meiosis
Fertilization
3. Describe and recognize the events of Meiosis
4. Describe similarities & differences between mitosis and meiosis.
5. Explain how meiosis contributes to genetic variation in sexually
reproducing organisms.
Egg cell
Multicellular
diploid adults
(2n = 46)
HUMAN
LIFE
CYCLE
Diploid
zygote
(2n = 46)
2n
Mitosis and development
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Diploid Organisms have Homologous Chromosomes
Karyotype
Homologous Chromosomes
Centromere
Sister chromatids
Figure 8.17A Differing genetic information on
homologous chromosomes
Coat-color
genes
Eye-color
genes
Brown
Black
C
E
Stages of Meiosis
Meiosis I
Meiosis II
Prophase I
Metaphase I
Anaphase I
Telophase I
Prophase II
Metaphase II
Anaphase II
Telophase II
Homologous
Pair
c
White
e
Pink
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5
Meiosis I - Prophase
Meiosis I: Prophase: Synapsis and Crossover
Synapsis
1. Chromosomes condense
2. Nuclear envelope
dissolves
Crossover
3. Centrioles move apart
4. Spindle apparatus forms
5. Synapsis - Homologous
chromosomes pair up
Homologous Chromosomes
after crossover
Animation
Meiosis I - Metaphase
Meiosis I - Anaphase
1. Homologous chromosomes
align in an equatorial plane
1. Homologous chromosomes
separate
2. Reduction division of
chromosomes where
2N Æ 1N
Figure 8.14 The stages of meiosis
Meiosis I - Telophase
1. Chromosomes decondense
2. Nuclear membrane forms
3. Spindle apparatus disappears
MEIOSIS I: Homologous chromosomes separate
INTERPHASE
Centrosomes
PROPHASE I
METAPHASE I
ANAPHASE I
Sister chromatids
Crossing over
Spindle
4. Cytokinesis – Two haploid
daughter cells form
Haploid Daughter Cells
Chromatin
Sister
chromatids
Homologous
chromosomes
pair up
Homologous
chromosomes
separate
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6
Figure 8.14 The stages of meiosis
Meiosis - Summary
MEIOSIS II: Chromatids separate
TELOPHASE I
AND CYTOKINESIS
PROPHASE II
METAPHASE II
ANAPHASE II
TELOPHASE II
AND CYTOKINESIS
Sister chromatids separate
Haploid daughter
cells form
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Figure 8.15 Comparison of mitosis and meiosis
MITOSIS
MEIOSIS
Parent cell
(before chromosome replication)
Figure 8.19 Preparation of a karyotype from a
blood sample
MEIOSIS I
Prophase I
Tetrad formed
by synapsis of
homologous
chromosomes
Chromosome
replication
Chromosome
replication
Duplicated
chromosome
(two sister chromatids)
2n = 4
Chromosomes
align at the
metaphase plate
Metaphase
Tetrads
align at the
metaphase plate
Hypotonic
solution
Blood
culture
Prophase
Metaphase I
2
2n
Daughter cells
of mitosis
2n
Homologous
chromosomes
separate during
anaphase I;
sister
chromatids
remain together
No further
chromosomal
replication; sister
chromatids
separate
during
anaphase II
3
Anaphase I
Telophase I
Haploid
n=2
Daughter
cells of
meiosis I
Homologous
chromosomes
MEIOSIS II
2,600×
Sister chromatids
separate during
anaphase
Stain
White
blood
cells
Centrifuge
1
Anaphase
Telophase
Fixative
n
n
n
n
Daughter cells of meiosis II
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Figure 8.21A Nondisjunction in meiosis I
Nondisjunction in
meiosis I
5
4
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Figure 8.21B Nondisjunction in Meiosis II
Normal meiosis I
Nondisjunction
in meiosis II
Normal
meiosis II
Gametes
Gametes
n+1
n+1
n−1
n−1
Number of chromosomes
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n+1
n−1
n
n
Number of chromosomes
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7
Figure 8.21C Fertilization after nondisjunction in the mother
Figure 8.20B A child with Down syndrome = Trisomy 21
1. Most common birth defect
2. 1 in 700
3. Physical features
Round face
Flattened nose bridge
Short stature
Heart defects
Egg cell
n+1
4. Susceptibility to infections
Zygote
2n + 1
n (normal)
Sperm cell
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Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Figure 8.20C Maternal age and incidence of Down
syndrome
Figure 8.22A A man with Klinefelter syndrome (XXY)
Poor beard
growth
Gamete from
Male Parent
Infants with Down syndrome
(per 1,000 births)
90
Breast
Development
80
Gamete from
Female Parent
XY
X
70
60
Under-developed
testes
50
XXY
40
30
20
10
0
20
25
30
35
40
50
45
Age of mother
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Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Figure 8.22B A woman with Turner syndrome (XO)
Figure 8.16
Web of
skin
Constriction
of aorta
Poor breast
development
Gamete from
Male Parent
Gamete from
Female Parent
Independent Assortment of chromosomes at metaphase I
Possibility 1
Possibility 2
Metaphase I Arrangements
O
X
XO
Metaphase II
Underdeveloped
ovaries
Gametes
Combination 1
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Combination 2
Combination 3
Combination 4
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8
END
Meiosis
9