Transcript The Cell Cycle

The Cell Cycle
Now Showing
at a science lab near you!
Limited engagement
A One Act Play
Directed by the nucleus
Produced by God
The Plot: one cell splits into two
identical smaller cells.
Purpose:
1. increase size of an organism
2. replace damaged cells
Starring
DNA
(played byTyler Perry)
The 3 faces of DNA
1.
2.
3.
Chromatin material – DNA as long
strands
Sister chromatids – DNA coiled tightly
and taking on the form of the letter X
Daughter chromosomes – Separated
sister chromatids looking like the letter V
DNA (Deoxyribose nucleic acid)
Model discovered by Watson & Crick
 Composed of 3 parts

 Sugar
(deoxyribose)
 Phosphate
 4 types of nucleotide bases




Adenine
Thymine
Guanine
Cytosine
Also starring
Centrioles
and
Spindle fibers
Overview of the Cell Cycle
Scene One
Interphase
Interphase
The period of time between cellular
divisions
 Time period for normal cellular
metabolism
 Composed of 3 parts

 G1
S
 G2
G1 part of Interphase
The first gap of Interphase
 Time period before the DNA is replicated
 Cell doubles in growth
 Cytoplasmic organelles replicate
 Time when the cell commits to cell division

S part of Interphase
Time period of DNA replication
 DNA unzips and new nucleotide bases are
laid down beside the original nucleotide
bases
 Results in 2 identical DNA structures

G2 part of Interphase
The second gap of Interphase
 Rapid cell growth
 Time period for synthesis of enzymes and
structures (asters & spindle fibers)
necessary for cell division
 Chromatin material checked for damage
(repairs made if necessary)

3 types of spindle fibers
Polar fibers – extend from centriole to
centriole
 Kinetochore fibers – extend from centriole
to centromere on a chromosome
 Asters – short fibers extending to the
outside of the centrioles

Interphase Picture
One more review of the cell cycle
Mitosis
Mitosis is part of the cell cycle, it is not
the cell cycle
 The following 4 scenes are the stages of
mitosis

Scene Two
Prophase
Prophase
Chromatin material coils so the
chromosomes look short, thick, and the
shape of an X (now called sister
chromatids)
 Nuclear envelope begins to disintegrate

Prophase
Centrioles begin moving apart and
towards opposite poles of the cell
 Sister chromatids begin moving to the
equator of the cell

Prophase Picture
Scene Three
Metaphase
Metaphase
Easiest stage to recognize!
 Kinetochore fibers pull sister chromatids
so they are lined up at the equator of the
cell

Metaphase Picture
Scene Four
Anaphase
Anaphase
Centromeres separate so the sister
chromatids are no longer X’s but are now
V’s (called daughter chromosomes)
 Kinetochore fibers pull daughter
chromosomes to a centriole
 Centromeres travel ahead and the
daughter chromosome arms travel behind
(creating the V shape)

Anaphase Picture
Scene Five
Telophase
Telophase
Daughter chromosomes arrive at the
opposite poles
 Daughter chromosomes unwind and are
referred to as chromatin material again
 Spindle fibers disintegrate
 Nuclear envelope reforms around the
chromatin material
 Cytokinesis occurs

Cytokinesis
Division of the cells’ cytoplasm
 Different for animals and plants

 Animals
– cell membrane pinches in to form a
cleavage furrow and divides the cell at the
center
 Plants – cell plate formed at equator of cell
and cellulose is laid on each side to create
new cell walls
Telophase Picture
Cytokinesis Picture
Cytokinesis Picture
One last look at the cell cycle
How well do you remember
the stages of the cell cycle?