Download Chapter 10 Cell Growth and Division-teacher

CHAPTER 10
CELL GROWTH
AND
REGULATION
AND
ASEXUAL
REPRODUCTION
KEY CONCEPT QUESTIONS:
• What are the main events of the cell
cycle?
• What happens during the four phases of
mitosis?
• What factor can stop cells from
growing?
• How is the cell cycle regulated?
• How are cancer cells different from
other cells
• What are the methods of asexual
reproduction?
Biology is the only subject in
which multiplication is the
same thing as division…
How do little elephants grow up to be BIG
elephants?
Why do animals shed their skin?
Where it all began…
You started as a cell smaller than
a period at the end of a sentence…
And now look at you…
How did you
get from there
to here?
In animals the process of asexual
reproduction (mitosis) begins after
a sperm fertilizes an egg.
Getting from there to here…
• Function of cell division
– making new cells
– continuity of life
• asexual reproduction
– unicellular organisms
• growth
• repair & renew
• Cell cycle
– life of a cell from
origin to division into
2 new daughter cells
CELL DIVISION
aka
MITOSIS
aka
ASEXUAL REPRODUCTION
• The process by which a cell divides
into two new daughter cells
• Before it becomes too large, a
growing cell divides into two
daughter cells.
Getting the right stuff
• What is passed on to daughter cells?
– exact copy of genetic material = DNA
• Every living organism has DNA, which
make up chromosomes.
• Each living organism has a certain
number of chromosomes
– fruit fly = 8
– carrot cells = 18
– human cells = 46
chromosomes (stained orange)
in kangaroo rat epithelial cell
notice cytoskeleton fibers
ONE CHROMOSOME
ONE COPIED CHROMOSOME
CENTROMERE
GENES
SISTER
CHROMATID
Sister
Chromatid
– each side of
a replicated
chromosome
SISTER
CHROMATID
Chromosome
• Duplicated
chromosome
consists of
2 sister
chromatids
– narrow at their
centromeres
– contain identical
copies of the
chromosome’s
DNA
BIOLOGY JOKE
• Q: How do you tell the sex of a
chromosome?
• A: Pull down its genes.
SAME DNA - JUST LOOKS DIFFERENT
CHROMATIN
–unwound
chromosomes;
not visible
CHROMOSOMES
–wound up DNA;
visible
CELL CYCLE
90% of cell
life cycle
•cell doing
its
“everyday
job”
INTERPHASE OCCURS BEFORE
MITOSIS BEGINS
• Chromosomes are copied (# doubles)
• Chromosomes appear as threadlike coils
(chromatin) at the start, but each
chromosome and its copy (sister
chromosome) change to sister chromatids
at end of this phase
NUCLEUS
CELL
MEMBRANE
CYTOPLASM
INTERPHASE
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• Divided into 3 phases:
– G1 = 1st Gap
INTERPHASE
• cell doing its
“everyday job”
• cell grows
– S = DNA Synthesis
• replicates
chromosomes
– G2 = 2nd Gap
• prepares for division
• cell grows
• produces organelles,
proteins, membranes
MITOSIS
• Dividing cell’s DNA between
2 daughter nuclei
– “dance of the chromosomes”
• 4 phases
– prophase
– metaphase
– anaphase
– telophase
http://www.cellsalive.com/mitosis.htm
PROPHASE
• chromosomes condense
• centrioles separate
– plant cells do not have
centrioles
• nucleolus disappears
• nuclear membrane breaks
down
• chromosomes become
attached to fibers called
spindle fibers at their
centromere
CENTRIOLES
• CENTRIOLES
– Two tiny structures located in the
cytoplasm near the nuclear envelope,
separate and take up positions on
opposite sides of the nucleus.
– Spindle fibers form from them.
• SPINDLE
– A fanlike microtubule structure that
helps separate the chromosomes.
– Attach from centriole to centromere.
PROPHASE
Animal Cell
Plant Cell
Spindle fibers
Centrioles
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase
• Chromosomes align along
middle of cell
– metaphase plate
• meta = middle
– spindle fibers coordinate
movement
– helps to ensure
chromosomes separate
properly
• so each new nucleus
receives only 1 copy of
each chromosome
METAPHASE
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
ANAPHASE
• Centromeres
separate and
chromatids are
pulled apart.
• Spindle reels in
the daughter
chromosomes to
either end of the
cell.
ANAPHASE
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
TELOPHASE
• Chromosomes arrive at
opposite poles
– daughter nuclei form
– nucleoli form
– chromosomes disperse
• no longer visible
under light
microscope
• Spindle fibers disperse
• Cytokinesis begins
– cell division
TELOPHASE
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
CYTOKINESIS
• The division of the
cytoplasm
• In animal cells – cell
membrane pinches in
until two cells are
formed
• In plant cells – cell
plate forms midway
between the two
nuclei – the cell wall
gradually appears
ONION ROOT TIP
MITOSIS IN ANIMAL CELLS
Coordination of cell division
• A multicellular organism needs to
coordinate cell division across different
tissues & organs
– critical for normal growth,
development & maintenance
• coordinate timing of
cell division
• coordinate rates of
cell division
• not all cells can have the
same cell cycle
Frequency of cell division
• Frequency of cell division varies by
cell type
– embryo
• cell cycle < 20 minute
– skin cells
• divide frequently throughout life
• 12-24 hours cycle
– liver cells
• retain ability to divide, but keep
it in reserve
• divide once every year or two
– mature nerve cells & muscle cells
• do not divide at all after
maturity
• permanently in G0
M
metaphase anaphase
telophase
prophase
C
G2
S
interphase (G1, S, G2 phases)
mitosis (M)
cytokinesis (C)
G1
Activation of cell division
• How do cells know when to divide?
– cell communication signals
• chemical signals in cytoplasm give cue
• signals usually mean proteins
– activators
– inhibitors
“Go-ahead” signals
• Protein signals that promote cell growth &
division
– internal signals
• “promoting factors”
– external signals
• “growth factors”
• How is the cell cycle regulated?
– Cyclins regulate the timing of
the cell cycle
• CYCLINS
– A protein that seems to regulate
the timing of the cell cycle
Cancer & Cell Growth
• Cancer is essentially a failure
of cell division control
– unrestrained, uncontrolled cell growth
Mutations in cells can be
triggered by
– UV radiation
– chemical
exposure
– radiation
exposure
– heat
– cigarette
smoke
– pollution
– age
– genetics
TUMORS
• Mass of abnormal cells
– Benign tumor
• abnormal cells remain at original site as
a lump
• most do not cause serious problems &
can be removed by surgery
– Malignant tumors
• cells leave original site
– start more tumors = metastasis
• impair functions of organs throughout
body
Traditional treatments for cancers
• Treatments target rapidly
dividing cells
– high-energy radiation
• kills rapidly dividing cells
– chemotherapy
• stop DNA replication
• stop mitosis & cytokinesis
• stop blood vessel growth
• Surgical removal of
the tumor
– remove the mass
and some of the
surrounding tissue
Methods of Asexual Reproduction
• Binary fission: equal division
of the cytoplasm and nucleus
of an organism resulting in
two mew organisms
– exs. ameba, paramecium,
euglena
• Budding: nucleus of an
organism's cell divides
equally but the cytoplasm
divides unequally
– the new cells formed may
live as individuals or as
colonies
• exs. yeast, hydra
YEAST BUDDING
• Sporulation: the production
of spores
– ex. molds
– spores: single, specialized
cells which are released
from the parent
– they are enclosed in a
protective case and
develop when
environmental conditions
are favorable
• Regeneration: the
development of an entire new
organism from part of an
original organism
– ex. starfish -- one ray and
part of central body
– may also involve the
restoration of lost body
parts
• Vegetative Propagation: regeneration in
plants
– Complete new plants develop from part
of the original plant.
Parthenogenesis
• Some crustaceans, such as water
fleas, reproduce by
parthenogenesis. Parthenogenesis
is a process in which a female
makes a viable egg that grows into
an adult without being fertilized
by a male.
KEY CONCEPT QUESTIONS:
• What are the main events of the cell
cycle?
– Interphase, mitosis, cytokinesis
• What happens during the four phases of
mitosis?
– Prophase
• chromosomes condense
• Centrioles separate
• Spindle fibers
KEY CONCEPT QUESTIONS
– Metaphase
• Sister chromatids line up in
middle of cell
– Anaphase
• Sister chromatids separate
– Telophase
• Nucleus reforms
• Chromosomes become chromatin
KEY CONCEPT QUESTIONS
• How is the cell cycle regulated?
– Chemicals called cyclins
• How are cancer cells different
from other cells?
– Cancer cells do not stop
dividing
KEY CONCEPT QUESTIONS
• What are some methods of asexual
reproduction?
– Binary fission
– Budding
– Sporulation
– Regeneration
– Vegetative propagation