The Great Divide
05/04
Why Would a Cell Divide?
 As cells absorb nutrients and get larger, the ______
of the cell increases faster than the _______ ____
 This means that a cell can no longer _________
and __________________ fast enough to support its
demands (volume)
 So what shall a cell do? DIVIDE !!!!
Why Would a Cell Divide?
Besides growth a cell would also divide for:
 R_________ or R__________
 C________
Different cells divide at different rates:
 Most mammalian cells = ______ hours
 Some bacterial cells = _______ minutes
Getting Older…
 All cells are only allowed to complete a
certain number of divisions
 Then they die (_________________________)
How does cell division change over a lifetime?
 Childhood =
 Adulthood =
 The Later Years =
Cell Cycle Tidbits
How long is one cell cycle?
 Depends on the cell- skin cells = ~__
hours, nerve cells = ______ after
maturity, cancer cells = _______
 Remember: every cell only has a
certain # of divisions it can undergo,
then it dies = _________ (programmed
cell death)
The Cell Cycle
Stages of the Cell Cycle
There are two stages to a cells life.
___________ (growth & replication of DNA)
____________ (division of cell into 2 daughter cells)
 Cell spends
about __% of
the time in
interphase
Interphase
 Divided into 3 phases:
 ____________ = small cell is absorbing nutrients,
growing & doing its job.
 ____________ = cell is continuing to grow &
duplicates its DNA.
 ____________ = cell keeps growing & doing its
job.
Mitosis: A Closer Look
DNA is all twisted up into a
Chromosome.
 During S phase the
Chromosomes are copied.
 2 complete identical sets
of chromosomes are
formed.
 They are connected in the
middle by a ___________.
 A single copied
chromosome is called a
__________.
The Mitotic Phase
 Divided into 4 stages of Mitosis:
 Prophase
 Metaphase
 Anaphase
 Telophase
(+) PLUS
 Cytokinesis
Prophase
 Chromatids ________
becoming ________.
 Nuclear membrane
_________
 The _________(an organelle
that makes microtubules)
appears and _________ to
opposite sides.
 ______________ start to form
between them
Metaphase
 Chromosomes
_______ on the
_______________
__________
 _________ are
attached to
spindle fibers
Anaphase
 Spindle fibers _______
 Centromeres ______
 Sister chromatids are
_____ ______from each
other ________________
Telophase
 The chromosomes
________________
 _______
___________ reform
around the 2 new
nuclei.
Cytokinesis
 The cytoplasm is
distributed equally
between the 2 new
cells
 In animals, a
___________ forms
from __________
 In plants, a ____
________ forms from
___________
Animal
Plant
What Mitosis Actually Looks Like
Interphase
Metaphase
Prophase
Anaphase
Telophase
http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_gif2.html
http://science.nhmccd.edu/biol/bio1int.htm
What Happens After Mitosis?
 The cell
returns to
________
 Chromosomes
______ back
into ________
 The cycle
repeats itself
over & over…
At What Stage Are Our Cells At In The Cell Cycle?
 Different cells can
be in different
stages
 Interphase
 Mitosis:
 Prophase
 Metaphase
 Anaphase
 Telophase
 Cytokinesis
The Guarantee
 The product of
mitosis is _______
 The daughter cells
are _______ to each
other & to the
mother cell
Why is this so
important?
Mother
cell
Identical
daughter
cells
The Daughter Cells
 In humans, the 2
daughter cells will have
____ chromosomes (___
pairs)
 Each chromosome is
said to have ____ _____
gene sequence
Identical
daughter
cells
The Beauty of Asexual Reproduction
 Mitosis is a
form of ______
___________
 New
individuals are
produced by 1
parent & thus,
are identical
to their parent
Mother
cell
Runners produces by
strawberries
Identical
Budding by hydra & yeast
daughter
cells
Cuttings from plants