Transcript The Cell Cycle

Cell Growth & Division
Chapter 5
AKS Standards:
8b - describe the cell cycle;
9e - compare the advantages of
sexual reproduction and asexual
reproduction in different situations
Functions of Cell Division
1. Reproduction of cells


all cells come from pre-existing cells
results in two identical cells except for size
2. Growth and Development of
Organisms

tadpoles become frogs, ivy vines get longer
3. Tissue renewal

skin cells are being replaced, cuts and bruises heal
Stages of the Cell Cycle


During the cell cycle, a cell grows, prepares for division,
and divides to form 2 identical daughter cells, where
each one of which begins a new cycle.
The 5 phases of the cell cycle are:
1.
Interphase (G1, S, G2) – period of rest between cell division
2.
Prophase
Metaphase
Anaphase
Telophase
3.
4.
5.
phases of nuclear
division (MITOSIS)
6. Cytokinesis - division of the cytoplasm
Events of the Cell Cycle
Gap 1 (G1): Cell carries out
normal functions. It also
increases in size and organelles
increase in number.
Synthesis (S): Cell makes a
copy of nuclear DNA.
Gap 2 (G2): Cells continue to
carry out normal functions and
prepares for Mitosis.
Mitosis (M): Includes nuclear
division and cytokinesis.
Cells Divide at Different Rates
 Rates of cell division vary widely, and each is linked
to a body’s need for those cells:
Limits to Cell Size
 Cells have upper and lower size limits.
 If they were too small, they could not contain all of the
necessary organelles and molecules.
 For example, a cell with only a few mitochondria would
not have enough energy to live.
 If they were too big, necessary nutrients and wastes
could not be transported efficiently into and out of cells.
 For example, wastes would collect inside the cell and
poison it; and nutrients could not reach organelles in a
timely manner, so cells would die.
 Also, information overload would occur. DNA makes
copies as a cell divides, and there must be enough DNA
blueprint to allow for protein production.
Review | Critical Thinking Activities
 The following activities are highly recommended by
your teacher. Each activity will allow you to (1) review
main concepts; (2) apply what you have learned; and (3)
think critically and analytically in such a way that allows
you to form your own conclusions in novel applications:



Section 5.1 Assessment Questions (textbook pp. 137).
Section 5.1 Concept Map: The Cell Cycle – accessed via the virtual
textbook at classzone.com.
Section 5.1 Virtual Quiz - accessed via the virtual textbook at
classzone.com.
AKS Standards:
8b - describe the cell cycle;
9e - compare the advantages of
sexual reproduction and asexual
reproduction in different situations
Cell Division: Distributing Identical Sets of
Chromosomes to Daughter Cells
 Cell division is the copying and
equal separation of chromosomes.
 Chromosomes are long
continuous threads of DNA that
consists of numerous genes along
with regulatory information:
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

made up of DNA and protein
cells of every organism have a specific
number of chromosomes
not visible in cells except during cell
division
Chromosome Structure
Diploid v. Haploid Cells
HAPLOID CELLS - gametes
DIPLOID CELLS - offspring
(single set of chromosomes)
(full set of chromosomes)
Cell Division
 Before it becomes too large, a
growing somatic cell divides
forming 2 “daughter” cells by a
process known as cell division:


The combined processes of mitosis
and cytokinesis produce two
genetically identical daughter cells.
Each daughter cell gets 1 complete
set of genetic information during cell
division and therefore will be
IDENTICAL TO THE MOTHER
CELL!
A somatic cell is a non sex cell!
Review: Events of the Cell Cycle
Interphase is divided into 3 phases:
1.
2.
3.
G1 – cell growth
S – DNA replication
G2 – preparation for Mitosis

During Interphase, chromosomes are in their “uncondensed” form and are called chromatin
Mitosis (nuclear division) is the division of the nucleus and it occurs
in 4 phases:
1.
2.
3.
4.
P = prophase – chromatin condenses into chromosomes, the
centrioles separate & nuclear membrane breaks down
M = metaphase – chromosomes line up across center of cell and
each chromosome is connected to a spindle fiber at its centromere
A = anaphase – sister chromatids separate into individual
chromosomes and are pulled apart
T = telophase – chromosomes gather at opposite ends of the cell
and 2 new nuclear membranes form around them
Cytokinesis – division of cytoplasm
INTERPHASE
• Nucleus well defined bounded by
nuclear envelope.
• Easily identifiable nucleolus.
• Genetic material in uncondensed
form of chromatin – chromosomes
cannot be seen.
Interphase is very long (cells spend most of time here):
G1 phase – cell growth; cells increase in size and synthesize new
proteins and organelles
S phase – chromosomes are replicated and the synthesis of DNA
molecules takes place; key proteins associated with the
chromosomes are synthesized during this time
G2 phase – shortest of 3 phases; many of the organelles and
molecules required for cell division are produced
M phase: Mitosis - PMAT
 Nuclear Division (Mitosis) is divided into
four phases:
Prophase
 Metaphase
 Anaphase
 Telophase
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
USEFUL ANIMATION:

http://www.sumanasinc.com/webcontent/animations/content/mi
tosis.html
PROPHASE
• Chromatin coils and condenses; becomes visible as
chromosomes.
• Centrioles separate and take up positions on opposite
sides of the nucleus.
• Chromosomes become attached to spindle fibers.
• Nucleolus disappears, nuclear membrane breaks down
Chromosome Duplication and Distribution During Mitosis
A duplicating chromosome
consists of 2 sister
chromatids, which narrow at
their centromeres. The DNA
molecules of sister
chromatids are identical.
Chromosomes normally
exist in the highly condensed
state shown here only during
the process of mitosis.
METAPHASE
• This is the shortest phase of mitosis.
• Chromosomes line up in center of cell along metaphase plate.
• For each chromosome, the kinetochores of the sister
chromatids are attached to microtubules coming from
opposite poles of the cell.
ANAPHASE
• Anaphase begins suddenly when the paired centromeres that
join the sister chromatids separate from each other.
• NOW EACH CHROMATID IS A SEPARATE
CHROMOSOME….they begin moving toward opposite poles
of the cell.
• Chromosomes continue to move until they have separated
into two groups near the poles of the spindle.
• Anaphase is over when the chromosomes stop moving!
TELOPHASE
• Two daughter nuclei form at the two poles of the cell.
• Chromosomes begin to relax back down into chromatin.
• Nuclear envelope re-forms around each cluster of
chromatin.
• Spindle begins to break apart and nucleolus reappears in
each daughter cell.
• NUCLEAR DIVISION IS NOW COMPLETE, BUT NOT
CELL DIVISION!
Phases of Mitosis
Cytokinesis
 Cytokinesis is the division of the cytoplasm
itself. It can take place in a number of ways:
 In
animal cells – “draw-string” effect forms cleavage
furrow (which pinches the cell into two parts).
 In
plant cells – cell plate forms from inside out, and
cell wall begins to appear .
Cytokinesis in Animal and Plant Cells
The stages of Mitotic Cell Division in an Animal Cell:
G2 phase; Prophase; Prometaphase
The Stages of Mitotic Cell Division in an Animal Cell:
Metaphase; Anaphase; Telophase and Cytokinesis.
Review | Critical Thinking Activities
 The following activities are highly recommended by
your teacher. Each activity will allow you to (1) review
main concepts; (2) apply what you have learned; and (3)
think critically and analytically in such a way that allows
you to form your own conclusions in novel applications:




Section 5.2 Assessment Questions (textbook pp. 142).
Animated Biology Activity: Mitosis Stage Matching Game –
accessed via the virtual textbook.
Section 5.2 Concept Map: Mitosis – accessed via the virtual
textbook at classzone.com.
Section 5.2 Virtual Quiz - accessed via the virtual textbook at
classzone.com.
AKS Standards:
8b - describe the cell cycle;
9e - compare the advantages of
sexual reproduction and asexual
reproduction in different situations
Regulation of the Cell Cycle
 Cell cycle regulation is necessary for
healthy growth.
 Cell growth and division are regulated
by both external factors, such as
hormones and growth factors, and
internal factors, such as proteins
known as cyclins and kinases.
 When proper regulated of cell growth
is disrupted, a cell may become
cancerous.
 Cancer cells grow more rapidly than do
normal cells and form clumps called
tumors that may metastasize to other
regions of the body.
Cell Division is Uncontrolled in Cancer
 Cancer is a common name for a class if diseases
characterized by uncontrolled cell division.
 Cancer cells form disorganized clumps called tumors.
 Cancer cells come from normal cells that have suffered
damage to the genes that help make proteins involved in
cell-cycle regulation.
 These mutations may be inherited, or they may be caused
by carcinogens (substances known to produce or
promote the development of cancer).
Review | Critical Thinking Activities
 The following activities are highly recommended by
your teacher. Each activity will allow you to (1) review
main concepts; (2) apply what you have learned; and (3)
think critically and analytically in such a way that allows
you to form your own conclusions in novel applications:




Section 5.3 Assessment Questions (textbook pp. 147).
WebQuest: Skin Cancer– accessed via the virtual textbook.
Section 5.3 Concept Map: Cell Cycle Regulation – accessed via the
virtual textbook at classzone.com.
Section 5.3 Virtual Quiz - accessed via the virtual textbook at
classzone.com.
AKS Standards:
8b - describe the cell cycle;
9e - compare the advantages of
sexual reproduction and asexual
reproduction in different situations
Asexual Reproduction
 Many organisms reproduce by cell
division.
 Most prokaryotes reproduce through a
process known as binary fission, in
which a cell divides into two
approximately equal parts.
 This is a type of asexual
reproduction whereby the offspring
are genetically identical to the parent
organism, except when mutation
occurs.
Review | Critical Thinking Activities
 The following activities are highly recommended by
your teacher. Each activity will allow you to (1) review
main concepts; (2) apply what you have learned; and (3)
think critically and analytically in such a way that allows
you to form your own conclusions in novel applications:




Section 5.4 Assessment Questions (textbook pp. 150).
Virtual Lab: Investigating Bacterial Growth – accessed via the
virtual textbook.
Section 5.4 Concept Map: Asexual Reproduction – accessed via the
virtual textbook at classzone.com.
Section 5.4 Virtual Quiz - accessed via the virtual textbook at
classzone.com.
AKS Standards:
8b - describe the cell cycle;
9e - compare the advantages of
sexual reproduction and asexual
reproduction in different situations
Multicellular Life
Cell Differentiation
Stem Cells
Review | Critical Thinking Activities
 The following activities are highly recommended by
your teacher. Each activity will allow you to (1) review
main concepts; (2) apply what you have learned; and (3)
think critically and analytically in such a way that allows
you to form your own conclusions in novel applications:





Section 5.5 Assessment Questions (textbook pp. 155).
Section 5.5 Concept Map: Multicellular Life – accessed via the
virtual textbook at classzone.com.
Section 5.5 Virtual Quiz - accessed via the virtual textbook at
classzone.com. Reviewing Vocabulary & Main Ideas (textbook pp.
159).
Critical Thinking & Connecting Concepts (textbook pp. 160)
GEORGIA Standards-Based Assessment (textbook pp. 161).