Download The Cell Cycle

The Cell Cycle
Cell Division in Prokaryotes:
Binary Fission
 Binary fission: The division of a bacteria cell into two offspring cells.
 1. The chromosome (single, circular, attached to the inside of
the cell membrane) which is attached to the inside of the
membrane makes a copy of itself. The copies stay attached to
the cell membrane.
 2. The cell continues to grow until it is about two times the cells
original cell.
 3. A cell wall forms between the two chromosomes and the
cell splits into two new cells.
 4. Each cell has one of the identical chromosomes that
resulted from the copying of the original cells chromosome.
Organization of Genetic
Material I
 All the DNA in a cell constitutes the cell’s genome
 A genome can consist of a single DNA molecule
(common in prokaryotic cells) or a number of DNA
molecules (common in eukaryotic cells)
 DNA molecules and proteins in a cell are packaged into
chromosomes
 Every eukaryotic species has a characteristic number of
chromosomes in each cell nucleus
 Somatic cells (non-reproductive cells) have two sets of
chromosomes
 Gametes (reproductive cells: sperm and eggs) have one set of
chromosomes
 Eukaryotic chromosomes consist of chromatin, a
combination of DNA and protein that condenses during
cell division
Distribution of Chromosomes
 In preparation for cell division, DNA is
replicated (DNA synthesis) and the
chromosomes condense (prophase)
 Each duplicated chromosome has
two sister chromatids, which
separate during cell division
 The centromere is the narrow “waist”
of the duplicated chromosome,
where the two chromatids are most
closely attached
 Eukaryotic cell division consists of:
 Mitosis, the division of the nucleus
 Cytokinesis, the division of the
cytoplasm
Chromosome Number and
Karyotypes
 Animals chromosomes are
catergorized as autosomes or sex
chromosomes
 Humans have 46 chromosomes.
 44 are autosomes
 2 are sex chromosomes
 Males are XY
 Females are XX
 Each individual gets two copies of
each type of chromosome. The two
copies are called homologous
chromosomes or homologues.
 Homologous chromosomes are
the same size and shape.
 They carry the genes for the same
trait.
 If one chromosome in a pair of
homologous chromosomes
carries the trait for nose shape,
so does the other chromosome
in the pair.
 Karyotypes: a picture of the
chromosomes in a dividing cell
found in a normal human.
 Karyotypes help us determine the
sex of an individual as well as if
there are any chromosome
number abnormalities.
Stages of the Cell Cycles
 The cell cycle consists of
 Interphase (cell growth and
copying of chromosomes in
preparation for cell division)
 About 90% of the cell cycle
 G1 phase (“first gap”)
 S phase (“synthesis”)
 G2 phase (“second gap”)
 The cell grows during all
three phases, but
chromosomes are
duplicated only during
the S phase
 Mitotic (M) phase (mitosis and
cytokinesis)
G1 – Growth 1of Interphase
 After a cell 1st divides, it is about ½ of the size it
should be. (awww… baby cell!)
 In G1 (G = growth or gap) the cell grows to a
mature size
 Under the right conditions, they will then proceed
to the S phase of interphase.
 Cells can also EXIT the cell cycle at this point and go
into a phase called G0
 In Go cells are mature, operating normally, but in
a non-dividing state.
 For example, all your nerve cells are in a G0 state.
S – Synthesis Phase of
Interphase
 This is the phase in which DNA is copied
 After the DNA is copied, the two copies will STAY
ATTACHED for awhile near the middle of each
strand. This will be important for the rest of cell
division.
G2 – Growth 2 of Interphase
 DNA is replicated, now the rest of the cell must
divide.
 G2 is the time when a cell prepares for cell
division.
Mitosis: The division of the
nucleus.
 Mitosis is divided into four phases:
 Prophase
 Metaphase
 Anaphase
 Telophase
 Cytokinesis, the division of the cytoplasm,
happens at the same time as telophase.
Mitosis: Prophase
 The chromatin condenses into
chromosomes.
 The two copies of the chromosomes (called
chromatids) are attached together at the
centromere
 The nuclear envelope starts to break down.
 The nucleolus disappears.
 Centrosomes, two dark spots, appear next
to the disappearing nucleus.
 The centrosomes start moving to opposite
sides (poles) of the cell forming spindle
fibers. The spindle fibers will help the
chromatids separate from each other.
Mitosis: Metaphase
 Chromosomes are fully
condensed.
 The spindle fibers are
attached to the
centromere of the
chromosomes.
 Chromosomes line up on an
imaginary line in the middle
of the cell called a
“metaphase plate”
 The centromeres line up
ON the metaphase plate.
Mitosis: Anaphase
 Chromatids of each
chromosome separate at
the centromere
 They are pulled to opposite
sides of the cell.
 When they separate, they
are considered to be full
chromosomes.
Mitosis: Telophase
 After the chromosomes reach
the opposite sides of the cell,
prophase is undone.
 The spindle fibers disassemble.
 The chromomoses uncoil and
return to chromatin
 The nuclueolus in each
daughter cell forms.
 Cytokinesis, the division of the
cytoplasm, is usually
happening at the same time.
Cytokinesis: The division of the cytoplasm.
Each cell formed by cytokinesis has ½ the
cytoplasm and ½ of the organelles of the
original cell.
Animal Cells
 The cell
membrane
pinches in ½ way
between the
dividing cells poles.
 This area is called
a cleavage furrow
 The cleavage
furrow eventually
separates the
cell into two
identical
daughter cells.
Plant Cells
 There is a cell wall
plants have to
deal with.
 Vesicles formed by
the Golgi
apparatus fuse in
the middle of the
cell to form a “cell
plate” (aww…
baby cell wall!)
 The cell plate will
grow until it
eventually divides
the cell into two
daughter cells.
BioFlix!
The Cell Cycle
Cell Division in Prokaryotes:
Binary Fission
 Binary fission: ______________________________________________________________________.
 1. The chromosome (single, circular, attached to the inside of the cell
membrane) which is attached to the inside of the membrane makes a copy of
itself. The copies stay attached to the cell membrane.
 2. The cell continues to grow until it is about two times the cells original cell.
 3. A cell wall forms between the two chromosomes and the cell splits into two
new cells.
 4. Each cell has one of the identical chromosomes that resulted from the copying
of the original cells chromosome.
Organization of Genetic
Material I
 All the DNA in a cell constitutes the cell’s ________________
 A genome can consist of a single DNA molecule
(common in prokaryotic cells) or a number of DNA
molecules (common in eukaryotic cells)
 _______________________________________ are packaged
into chromosomes
 Every eukaryotic species has a characteristic number of
chromosomes in each cell nucleus
 Somatic cells (non-reproductive cells)
______________________________________________________
 Gametes (reproductive cells: sperm and eggs) have one set of
chromosomes
 Eukaryotic chromosomes consist of _____________________,
a combination of DNA and protein that condenses during
cell division
Distribution of Chromosomes
 In preparation for cell division, DNA is
replicated (DNA synthesis) and the
chromosomes condense (prophase)
 Each duplicated chromosome has
two __________________________,
which separate during cell division
 The centromere
___________________________________
______________________________,
where the two chromatids are most
closely attached
 Eukaryotic cell division consists of:
 Mitosis,
___________________________
 Cytokinesis,
_________________________________
Chromosome Number and
Karyotypes
 Animals chromosomes are
catergorized as autosomes or sex
chromosomes
 Humans have 46 chromosomes.
 44 are autosomes
 2 are sex chromosomes
 Males are XY
 Females are XX
 Each individual gets two copies of
each type of chromosome. The two
copies are called homologous
chromosomes or homologues.
 Homologous chromosomes are
the same size and shape.
 They carry the genes for the same
trait.
 If one chromosome in a pair of
homologous chromosomes
carries the trait for nose shape,
so does the other chromosome
in the pair.
 Karyotypes:
___________________________________
___________________________________
__________________________________.
 Karyotypes help us determine the
sex of an individual as well as if there
are any chromosome number
abnormalities.
Stages of the Cell Cycles
 The cell cycle consists of
 _______________________ (cell
growth and copying of
chromosomes in preparation
for cell division)
 About 90% of the cell cycle
 G1 phase (“first gap”)
 S phase (“synthesis”)
 G2 phase (“second gap”)
 The cell grows during all
three phases, but
chromosomes are
duplicated only during
the S phase
 ______________________ (mitosis
and cytokinesis)
G1 – Growth 1of Interphase
 After a cell 1st divides, it is about ½ of the size it
should be. (awww… baby cell!)
 In G1 (G = growth or gap)
_________________________________________________
 Under the right conditions, they will then proceed to
the S phase of interphase.
 Cells can also EXIT the cell cycle at this point and go
into a phase called G0
 In Go cells are mature, operating normally, but in a
non-dividing state.
 For example, all your nerve cells are in a G0 state.
S – Synthesis Phase of
Interphase
 ________________________________________________
 After the DNA is copied, the two copies will STAY
ATTACHED for awhile near the middle of each
strand. This will be important for the rest of cell
division.
G2 – Growth 2 of Interphase
 DNA is replicated, now the rest of the cell must
divide.
 ________________________________________________
________________________________________________
Mitosis: The division of the
nucleus.
 Mitosis is divided into four phases:
 _________________
 _________________
 _________________
 _________________
 Cytokinesis, the division of the cytoplasm,
______________________________________________.
Mitosis: Prophase
 __________________________________________
__________________________________________.
 The two copies of the chromosomes (called
chromatids) are attached together at the
centromere
 __________________________________________.
 The nucleolus disappears.
 Centrosomes, two dark spots, appear next
to the disappearing nucleus.
 The centrosomes start moving to opposite
sides (poles) of the cell forming spindle
fibers. The spindle fibers
________________________________________
________________________________________
________________________________________
Mitosis: Metaphase
 Chromosomes are fully
condensed.
 The spindle fibers are
attached to the
centromere of the
chromosomes.
 ___________________________
___________________________
___________________________
 The centromeres line up
ON the metaphase plate.
Mitosis: Anaphase
 ___________________________
___________________________
___________________________
 ___________________________
___________________________
___________________________
 When they separate, they
are considered to be full
chromosomes.
Mitosis: Telophase
 _____________________________
_____________________________
____________________________.
 The spindle fibers disassemble.
 The chromomoses uncoil and
return to chromatin
 The nuclueolus in each
daughter cell forms.
 Cytokinesis, the division of the
cytoplasm, is usually
happening at the same time.
Cytokinesis: The division of the cytoplasm.
Each cell formed by cytokinesis has ½ the
cytoplasm and ½ of the organelles of the
original cell.
Animal Cells
 __________________
__________________
__________________
__________________
__________________.
 __________________
__________________
 The cleavage
furrow eventually
separates the
cell into two
identical
daughter cells.
Plant Cells
 There is a cell wall
plants have to
deal with.
 Vesicles formed by
the Golgi
apparatus fuse in
the middle of the
cell to form a “cell
plate” (aww…
baby cell wall!)
 __________________
__________________
__________________
__________________.