Transcript Document

1.2 Eukaryotic Cell Growth and
the Cell Cycle
1.2 Cell Growth and
the Cell Cycle
Two Stages:
INTERPHASE – G1, S, G2
MITOSIS (incl. CYTOKINESIS)
INTERPHASE
The cell is preparing for mitosis.
Chromosomes are not clearly visible in the
nucleus.
Nuclear membrane intact.
When complete cell is ready for mitosis
MITOSIS

PROPHASE
Chromosomes condense, become visible.
Nucleolus disappears.
Centrioles start to migrate to opposite ends
of cell
Fibres extend from centrioles across the cell
to form the mitotic spindle (made of
microtubules).
Chromosomes start to condense and appear
MITOSIS

PROMETAPHASE
The nuclear membrane dissolves, marking
the beginning of prometaphase.
The chromosomes attach to spindle fibres
and begin moving.
MITOSIS

METAPHASE
Spindle fibres align the chromosomes along
the middle of the cell nucleus - metaphase
plate.
MITOSIS

ANAPHASE
Spindle fibre contracts, separating the
chromatids, moving them to opposite poles
of the cell.
MITOSIS

TELOPHASE
New membranes form around the daughter
nuclei.
The chromosomes disperse and are no longer
visible, nucleoli reappear
The spindle fibres disperse
Cytokinesis or the partitioning of the cell
may also begin during this stage.
Mitosis Practice sheets




http://www.biology.arizona.edu/cell_b
io/activities/cell_cycle/01m.html classifying stages of mitosis
http://biog-101104.bio.cornell.edu/BioG101_104/tut
orials/cell_division/CDCK/cdck.html
Cell division construction kit
http://www.cellsalive.com/cell_cycle.
html -
CYTOKINESIS
In animal cells,
Ring of actin around centre of cell contracts,
pinching the cell into two daughter cells,
each with one nucleus.
In plant cells,
A cell plate is synthesized between the two
daughter cells as the cell wall extends, the
cell membrane is laid down on either side of
it.
Web pages



http://www.biology.arizona.edu/cell_bio/tutorials/c
ell_cycle/cells.html - clear and at the level
required.
http://www.biology.arizona.edu/cell_bio/activities/c
ell_cycle/01m.html - classifying stages of mitosis
http://www.cellsalive.com/cell_cycle.html -
The nucleus - membrane bound organelle that
contains the genetic information in the form of
chromatin, highly folded ribbon-like complexes
of DNA and a class of proteins called histones.
When a cell divides, chromatin fibers are very
highly folded, and become visible in the light
microscope as chromosomes. During interphase
(between divisions), chromatin is more extended,
a form used for expression genetic information.
The DNA of chromatin is wrapped around a
complex of histones making what can appear in
the electron microscope as "beads on a string" or
nucleosomes. It is the packaging of these
nucleosomes which is responsible for
condensing of chromsosomes during the first
stage of mitosis (prophase).
Cell Cycle
G1 stage stands for "GAP 1".
The S stage stands for "Synthesis, when DNA replication
occurs.
G2 stage stands for "GAP 2“
M stage stands for "mitosis", and is when nuclear
(chromosomes separate) and cytoplasmic (cytokinesis)
division occur.