Download CHAPTER 8 The Cellular Basis of Reproduction

CHAPTER 8
The Cellular Basis of
Reproduction and Inheritance
Biology is the only subject in
which multiplication is the same
thing as division…
2006-2007
CONNECTIONS BETWEEN CELL
DIVISION AND REPRODUCTION

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Cell division is at the heart of the
reproduction of cells and organisms
Organisms can reproduce sexually or
asexually
Like begets like, more or less


Some organisms make
exact copies of
themselves, asexual
reproduction
Other organisms make
similar copies of
themselves in a more
complex process,sexual
reproduction
Prokaryotes reproduce by binary fission

Prokaryotic cells
divide asexually

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These cells possess a
single chromosome,
containing genes
The chromosome is
replicated
The cell then divides
into two cells, a process
called binary fission
Duplication of chromosome
and separation of copies
Continued growth of the
cell and movement of
copies
Division into
two cells
THE EUKARYOTIC CELL CYCLE
AND MITOSIS

A eukaryotic cell has
many more genes than
a prokaryotic cell

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The genes are grouped
into
multiple chromosomes,
found in the nucleus
The chromosomes of this
plant cell are stained
dark purple
The large, complex chromosomes of
eukaryotes duplicate with each cell
division

Chromosomes contain a very
long DNA molecule with
thousands of genes

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Individual chromosomes are
only visible
during cell division
They are packaged as
chromatin
Before a cell starts
dividing, the
chromosomes are
duplicated

This process produces sister
chromatids
Sister chromatids
Centromere
double-stranded
human chromosomes
ready for mitosis
The large, complex chromosomes of
eukaryotes duplicate with each cell
division

When the cell
divides, the sister
chromatids separate


Two daughter cells
are produced
Each has a complete
and identical set of
chromosomes
Chromosome
duplication
Sister
chromatids
Chromosome
distribution
to
daughter
cells
The Cell Cycle


The cell cycle is the
sequence of growth and
division of a cell. Duration
varies with cell type
The cell cycle consists of two
Interphase
major phases:


Interphase, where
chromosomes duplicate
and cell parts
are made
The mitotic
phase, when
cell division
occurs
Interphase: A Busy Time

Interphase, the busiest phase of the cell cycle, is
divided into three parts.
Interphase
DNA synthesis and
replication
Rapid
growth and
metabolic
activity
cell prepares
for division
Cell division is a continuum of
dynamic changes

Eukaryotic cell division
consists of two stages:


Mitosis~ process during
which duplicated
chromosomes are
separated into 2 nuclei
Cytokinesis ~ entire cell
divides into 2 daughter
cells
MITOSIS:
Making New Cells
Making New DNA
Where it all began…
You started as a cell smaller than
a period at the end of a sentence…
Getting from there to here…

Going from egg to baby….
the original fertilized egg has to divide…
and divide…
and divide…
and divide…
Why do cells divide…
 One-celled organisms

for reproduction

asexual reproduction (clones)
amoeba
 Multi-celled organisms

for growth & development
 from fertilized egg to adult

for repair & replacement
 replace cells that die from
normal wear & tear or from injury
starfish
Mitosis
Mitosis
Mitosis in whitefish blastula
Mitosis in plant cell
onion root tip
8.7 Cytokinesis differs for
plant and animal cells

In animals,
cytokinesis occurs
by cleavage


This process pinches
the cell apart
In plants, a
membranous cell
plate splits the cell
in two
Overview of mitosis
interphase
I.P.M.A.T.C.
prophase
Please Make Another Two
Cells
cytokinesis
metaphase
anaphase
telophase
New “daughter” cells

Get 2 exact copies of original cells


same DNA
“clones”
8.8 Anchorage, cell density, and
chemical growth factors affect cell division

In laboratory cultures, most
normal cells divide only
when attached to a surface

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They are anchorage
dependent
Cells continue dividing until
they touch one another
This is called density-dependent
inhibition

Growth factors are proteins
secreted by cells that
stimulate other cells to
divide
8.9 Growth factors signal the cell
cycle control system

Proteins called cyclins within the cell control the cell cycle

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Signals affecting critical checkpoints determine whether the cell will
go through a complete cycle and divide
The binding of growth factors to specific receptors on the
plasma membrane is usually necessary for cell division
8.10 Connection: Growing out of control,
cancer cells produce malignant tumors

Cancer cells have abnormal cell cycles

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They divide excessively and can form abnormal masses
called tumors
Radiation and chemotherapy are effective as cancer
treatments because they interfere with cell division
Cancer:
breast cancer cell &
mammogram
Traditional treatments for
cancers

Treatments target rapidly dividing cells

high-energy radiation

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kills rapidly dividing cells
chemotherapy

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stop DNA replication
stop mitosis & cytokinesis
stop blood vessel growth
New “miracle drugs”

Drugs targeting proteins (enzymes) found
only in cancer cells

Gleevec

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treatment for adult leukemia (CML)
& stomach cancer (GIST)
1st successful drug targeting only cancer cells
without
Gleevec
Novartes
with
Gleevec
Cancer: A mistake in the Cell Cycle

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Currently, scientists consider cancer to be a
result of changes in one or more of the genes
that produce substances that are involved in
controlling the cell cycle.
Cancerous cells form masses of tissue called
tumors that deprive normal cells of nutrients
Cancer: A mistake in the Cell Cycle

In later stages, cancer cells enter the circulatory
system and spread throughout the body, a process
called metastasis, forming new tumors that disrupt
the function of organs, organ systems, and
ultimately, the organism.
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The causes of cancer
The causes of cancer are
difficult to pinpoint because
both genetic and
environmental factors are
involved.
Environmental factors, such
as cigarette smoke, air and
water pollution, and
exposure to ultraviolet
radiation from the sun, are
all known to damage the
genes that control the cell
cycle.
Cancer may also be caused
by viral infections that
damage the genes.
Cancer prevention

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Physicians and dietary
experts agree that diets low
in fat and high in fiber
content can reduce the risk
of many kinds of cancer.
Vitamins and minerals may
also help prevent cancer.
In addition to diet, other
healthy choices such as daily
exercise and not using
tobacco also are known to
reduce the risk of cancer.