Transcript CellularBasisofReproductionandInheritancePart1STUDENT20122013

CHAPTER 8 – CELLULAR
REPRODUCTION: CELLS
FROM CELLS part I
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Introduction to Cell Division Review
1. Daughter cells formed
during cell division have
2. True or False? Growth of
a)
identical sets of
chromosomes with
identical genes.
an organism and the
replacement of lost or
damaged cells are the main
roles of cell division.
b)
different sets of
chromosomes with
identical genes.
3. Before a cell divides, it
duplicates its _______.
c)
identical sets of
chromosomes with
different genes.
d)
different sets of
chromsomes with different
genes.
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4. Sexual reproduction
a. uses only meiosis.
b. involves the production
of daughter cells with
double the genetic
material of the parent
cell.
c. uses only ordinary cell
division.
d. requires the fertilization
of an egg by a sperm.
e. is the normal process by
which the cells of most
organisms divide.
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5. True or False? A sperm
or egg has twice as
many chromosomes as
its parent cell.
6. In _____ reproduction,
the offspring and parent
have identical genes.
• The life cycle of a multicellular
organism includes
– development
– reproduction
• This sea star embryo (morula) shows one stage
in the development of a fertilized egg
– The cluster of cells will continue to divide as
development proceeds
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Introduction to Cell Division
Life cycle – the sequence of life stages leading
from the adults of one generation to the adults
of the next
• Development phase – fertilized egg to a new
adult organism
• Reproduction phase – formation of new
individuals from preexisting ones
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CONNECTIONS BETWEEN CELL DIVISION
AND REPRODUCTION
• Cell division is at the heart of the reproduction
of cells and organisms
• Organisms can reproduce sexually or asexually
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In asexual reproduction, single-celled organisms
reproduce by simple cell division.
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• Some multicellular organisms can divide into
pieces that then grow into new individuals.
– This sea star is regenerating a lost arm
– Regeneration results from repeated cell
divisions
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Like begets like, more or less
• Some organisms make exact copies of
themselves, asexual reproduction
Figure 8.1A
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• Other organisms make similar copies of
themselves in a more complex process, sexual
reproduction
Figure 8.1B
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Introduction of Cell Division
• Sexual reproduction – process that involves the
union of a sperm and egg
• Asexual reproduction – production of offspring
by a single parent
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Comparing Asexual and Sexual Reproduciton
2 minutes work independently
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Comparing Asexual and Sexual Reproduciton
Quietly Share W/ your Partner
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Cells arise only from preexisting cells
• All cells come from cells
• Cell division – the process by which cells
reproduce
• Main roles:
– The development of a fertilized egg to an adult,
how organisms grow to adult size
– Replaces worn out and damaged cells
– Asexual reproduction or the formation of eggs
and sperm
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Prokaryotes reproduce by binary fission
• Prokaryotic cells divide asexually
– These cells possess a single chromosome, containing
genes
– The chromosome is replicated
– The cell then divides into two cells, a process called
binary fission
Prokaryotic chromosomes
Figure 8.3B
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• Binary fission of a prokaryotic cell
Plasma
membrane
Prokaryotic
chromosome
Cell wall
Duplication of chromosome
and separation of copies
Continued growth of the cell
and movement of copies
Division into
two cells
Figure 8.3A
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Chromosomes
• Almost all of the genes of a
eukaryotic cell are located on
chromosomes in the cell
nucleus.
– Chromosome – DNA
containing structure found
in the nucleus of an
eukaryotic cell. It carries the
organism’s genetic
information
– Gene – a unit of hereditary
information consisting of a
specific nucleotide sequence
of DNA
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Eukaryotic Chromosomes
• Each eukaryotic
chromosome contains
– one very long DNA
molecule carrying
thousands of genes.
– Proteins – help organize
the DNA and control the
activity of the genes
• The number of
chromosomes in a
eukaryotic cell depends
on the species.
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Figure 8.3
Chromosomes
• Chromosomes can exist as
– Chromatin – mass of very long, very thin fibers made up of DNA and
protein
– Compact, distinct structures that are visible under the light microscope.
Occur when the cell is dividing.
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• Before a cell starts
dividing, the
chromosomes are
duplicated
– This process
produces sister
chromatids - 2
exact copies of the
DNA
– Centromere –
where the 2 sister
chromatids are
joined
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Sister chromatids
Centromere
Figure 8.4B
• When the cell
divides, the sister
chromatids separate
Chromosome
duplication
– Two daughter
cells are produced
– Each has a
complete and
identical set of
chromosomes
Sister
chromatids
Centromere
Chromosome
distribution
to
daughter
cells
Figure 8.4C
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Cell cycle
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Lecture review
1. Which of the following is
false?
a. The number of
chromosomes in a
eukaryotic cell depends
on the species
2. True or False? The
lipids in chromosomes
help control the activity
of the genes
3. Sister chromatids are
attached at a region
called the ________.
b. Chromosomes are made
up of DNA, carbohydrates
and lipids
4. Prokaryotic organisms
c. Human body cells have
46 chromosomes
reproduce mainly by
_________.
5. What are the 3 roles of
d. When separated sister
cell division?
chromatids go to different
cells
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DNA Replication
DNA Replication
• The process by which a new molecule of DNA is
formed.
• Origins of replication – the specific sites on the
DNA where DNA replication begins.
– Enzymes attach to the origins of replication and
break the hydrogen bonds between the bases
– Causes the 2 DNA strands to separate
– Creates a replication bubble
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
DNA Replication
• The separated strands act as a
template to create the new
complementary strands
• Only adds nucleotides to the 3’
end of the growing strand
Old Strand
– DNA polymerase adds the new
DNA nucleotides
New Strand
– New nucleotides are added to the
bases of each parent strand
Add next
nucleotide here
• The new strand only grows from
the 5’ to 3’ direction
http://homepage.smc.edu/hgp/images/dna-rep-small.gif
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DNA Replication
•
One strand is synthesized in one continuous piece – leading strand
• Other strand is synthesized in pieces – lagging strand
• DNA ligase joins the pieces in the lagging strand
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DNA Replication
• Once daughter strands are completed DNA
polymerase checks for any errors and corrects
them (proofreads)
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DNA Replication
Result of DNA Replication
• 2 DNA molecules are formed that are exactly
alike
• Each DNA molecule contains
– 1 nucleotide chain from the original DNA
– 1 new nucleotide chain formed during
replication
– This makes DNA replication semi-conservative
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Quick Write
• Describe the process of DNA replication.
– Include all of the following terms
• DNA polymerase
• Origin of replication
• Helicase
• Leading strand
• Lagging strand
• Okazaki fragments
• Ligase
• Semiconservative replication
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The Cell Cycle
Cell cycle – orderly
sequence of events that
occur from the
formation of a new cell
by division to that cell
dividing.
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The cell cycle multiplies cells
• The cell cycle consists of two major phases:
– Interphase, where chromosomes duplicate
and cell parts
are made
– The mitotic
phase, when
cell division
occurs
Figure 8.5
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The Cell Cycle
The cell cycle can be divided
into:
1.
Interphase
a. G1 phase – the cell
increases in size, the number
of organelles and proteins
increase
b. S phase – DNA duplicates
c. G2 phase – period of rapid
growth, cell prepares to
divide by producing the
proteins needed for cell
division.
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2.
The Cell Cycle
Mitotic Phase – two
daughter cells are
produced that are identical
to one another.
a. Mitosis
- the division of the nucleus
and its contents
- the duplicated chromosomes
are separated and evenly
distributed to form 2
daughter nuclei
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The Cell Cycle
Interphase
• Chromosomes not
visible – in the form of
chromatin
• Nucleus visible
• Nucleus contains 1 or
more nucleoli
• Centrosomes have
duplicated
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• Stages of Mitosis: animation from CD rom
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Write the name of the stage of the cell cycle being described?
1. ________ The chromosomes are lined up in
the middle of the cell
2. ________ The 2 groups of chromosomes
have reached the cell poles
3. ________ Period of cell growth
4. ________ Mitotic spindle is fully formed
5. ________ Sister chromatids of each
chromosome separate
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Write the name of the stage of the cell cycle being described?
6. ________ The nuclear envelope breaks up
7. ________ The chromosomes are duplicated
8. ________ Daughter chromosomes are
“walked” by motor proteins toward opposite
poles
9. ________ Chromosomes uncoil
10. _______ Each chromosome appears
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The Cell Cycle
b. Cytokinesis – the division of the cytoplasm
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Cytokinesis differs for plant and animal cells
• In animals, cytokinesis
occurs by cleavage
Cleavage
furrow
– This process pinches
the cell apart
Cleavage
furrow
Figure 8.7A
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Contracting ring of
microfilaments
Daughter cells
• In plants, a
membranous cell
plate splits the cell in
two
Cell plate
foring
Wall of
parent cell
Daughter
nucleus
New cell wall
Figure 8.7B
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Vesicles containing
cell wall material
Cell plate
Daughter
cells
• Cells continue dividing until they touch one
another
– This is called density-dependent inhibition
Cells anchor to dish surface and
divide.
When cells have formed a
complete single layer, they stop
dividing (density-dependent
inhibition).
If some cells are scraped away,
the remaining cells divide to fill
the dish with a single layer and
then stop (density-dependent
inhibition).
Figure 8.8A
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Anchorage, cell density, and chemical growth
factors affect cell division
• Most animal cells divide only when stimulated,
and others not at all
• In laboratory cultures, most normal cells divide
only when attached to a surface
– They are anchorage dependent
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• Growth factors are proteins secreted by cells
that stimulate other cells to divide
– Density dependent inhibition may be due to an
inadequate supply of growth factor
After forming a single layer, cells
have stopped dividing.
Providing an additional supply of
growth factors stimulates further
cell division.
Figure 8.8B
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Growth factors signal the cell cycle control system
• Growth factors within the cell control the cell
cycle
– Signals affecting critical checkpoints determine
whether the cell will go through a complete cycle
and divide
G1 checkpoint
Control
system
M checkpoint
G2 checkpoint
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Figure 8.9A
Growth factors control the cell cycle at 3 key
checkpoints
1. In the G1 phase – for many cells this is the
most important
2. In the G2 phase
3. In the M (metaphase) phase
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Growing out of control, cancer
• Cancer cells have abnormal cell cycles
– They divide excessively and can form abnormal
masses called tumors
– Are unrestrained by the systems that normally
control cell division
• Not affected by density dependent inhibition
• Don’t need growth factors to move past
checkpoints
• Synthesize own growth factors
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Figure 11.20b
Cancer
Tumor – an abnormal mass of cells due to
excessive growth
- benign
abnormal mass of normal cells
stay at original site
don’t usually impair normal function
can be completely removed by surgery
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Cancer
malignant
– mass of cancer cells
- can spread to other tissues and parts of
the body
- can impair normal function of tissue,
organ
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Figure 11.20a
• Malignant tumors can invade other tissues and
may kill the organism
Lymph
vessels
Tumor
Glandular
tissue
Metastasis
1
A tumor grows
from a single
cancer cell.
2
Cancer cells invade
neighboring tissue.
Figure 8.10
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3
Cancer cells spread
through lymph and
blood vessels to other
parts of the body.
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Table 11.1
Cancer
Cancer Treatment
Radiation – expose cancerous tumors to high
energy radiation which disrupts cell division
Chemotherapy – drugs are administered that
disrupt cell division
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Cancer Prevention/ Early Identification
• Self Examination
– Breast
– Testicular
– Skin
• Healthy Lifestyle
– Sunblock
– Avoid tobacco, drugs
– Balanced diet
– Exercise
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• Medical Tests
– Pap smear
– Colonoscopy