Cell Cycle
Life of a Eukaryotic Cell
Cell Cycle
 (Interphase in Red)
 G1 – cell grows & carries out
major functions
 S – DNA is copied
 G2 – Prep for mitosis;
organelles reproduced
 Mitosis – Nucleus divided into
two nuclei, each with same
number and kind of
chromosomes
 Cytokinesis – cytoplasm
divides
Cell Cycle Control
 How does cell “know” when to divide?
 Cell cycle controlled by many proteins (enzymes) at
three main checkpoints:
 G1 checkpoint – decision made whether cell will divide
(cell healthy and large enough). Some types of cell never
pass this point (nerve, muscle)
 G2 checkpoint – Did DNA replication go OK? If so, go on
to mitosis
 Mitosis checkpoint – Is mitosis over? If so, head to G1
phase
Cancer - What happens if
control is lost
 Cancer = uncontrolled cell
 Mutations:
growth
 Disorder of cell division
 Control mechanisms don’t
work (gene for proteins that
control cell cycle are
defective)
 Overproduction of growthpromoting hormones –
speeds up cell cycle
 Inactivation the control
proteins that act to slow or
stop cell cycle
Mitosis and Cytokinesis
 Chromatids are physically
moved to opposite sides of
dividing cells with help of
spindle fibers
 Centrosome (in animals) –
made up of two centrioles organizes assembly of
spindle fibers
 Spindle fibers made from
microtubules
Mitosis and Cytokinesis
 Chromatids separate by
attaching spindle fibers
 Spindle fibers attach to
centromeres of
chromosomes
 Paired chromatids separate.
One chromatid goes to one
pole of the cell, the other
chromatid goes to the other
as the spindle fibers shorten
Interphase (90% of cell’s time)
Mitosis (nuclear division)
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis (cytoplasmic division)
Watch video clip of mitosis
Another View of Mitosis
Mitosis Foldable
 6 sheets of paper
 Follow teacher’s instructions to construct booklet
 You will make foldable based on pictures and
descriptions of interphase, cyokinesis, and mitosis in
your book (p. 125 and pp 130 – 132)
 Include sketches and textual descriptions in foldable
 You can also use www.cellsalive.com and
www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/m
ain.html
Headings for foldable
 Cover = Phases of Somatic Cell Division
 Following sheets –
 Interphase
 G1
 S
 G2
 Mitosis




Prophase
Metaphase
Anaphase
Telophase
 Cytokinesis
Homework
 Read Ch. 7 – “Meiosis and Sexual Reproduction”
 Also read about plant reproduction pp. 534 – 535, and
pp. 538 – 539
 Complete Guided Reading packet for Chapter 7
 Complete Foldable