Transcript CELL DIVISION

CELL DIVISION
Key Concepts
• What events take place during the
three stages of the cell cycle?
Key Terms
• cell cycle –
• The regular sequence of
growth and division that
cells undergo.
• interphase –
• The stage of the cell cycle
that takes place before
cell division occurs.
• replication –
• The process by which a
cell makes a copy of the
DNA in its nucleus.
Key Terms
• mitosis –
• The stage of the cell cycle during
which the cell’s nucleus divides
into two new nuclei and one copy
of the DNA is distributed into each
daughter cell.
• chromosome –
• A double rod of condensed
chromatin; contains DNA that
carries genetic information.
• cytokinesis –
• The final stage of the cell cycle, in
which the cell’s cytoplasm divides,
distributing the organelles into
each of the new cells.
Introduction
•A multicellular
organism
grows in size
because it’s
cells are
increasing in
number.
Three Stages of Cell Division
• Stage 1: Interphase
• The period before
cell division.
• Stage 2: Mitosis
• One nucleus
divides to create
two.
• Stage 3: Cytokinesis
• Completes the
process of cell
division.
Stage 1: Interphase
The period before cell division.
The Resting Stage?
• Growing
– The cell grows to full
size.
– The cell makes new
structures it needs or
duplicates others.
• Copying DNA
– A replication (exact
copy) for the new cell is
made.
• Preparing for Division
– Centrioles (structures
used for cell division)
are made.
Stage 2: Mitosis
One nucleus divides to create two.
It’s All About the . . .
CHROMOSOMES!
The Many “Faces” of A
Chromosome
• Chromatin (threadlike)
– A mass of genetic material
composed of DNA and
proteins that condense to
form chromosomes.
CHROMATIN
• Chromosome (letter X)
– A condensed, double-rod,
form of chromatin.
• Chromatid
– Two identical strands of
DNA that form a
chromosome.
• Centromere
– A structure that holds the
chromatids together.
CHROMOSOME
Phase 1: Prophase
• Chromosomes and
spindle fibers form.
• Nuclear envelope
(membrane) breaks
down.
Phase 2: Metaphase
• Chromosomes line
up across the
center and attach
to a spindle fiber.
Phase 3: Anaphase
• Centromeres split.
• Chromatids
separate and move
to opposite ends.
Phase 4: Telophase
• Chromosomes
stretch out.
• New nuclear
envelope
(membrane) forms
around
chromosomes.
Stage 3: Cytokinesis
Completes the process of cell division.
Like Mother Like Daughter
• Cell pinches in two.
• Each daughter cell
has the same
number of
identical
chromosomes.
Animal Cells vs. Plant Cells
• The cell membrane
squeezes together around
the middle of the cell.
• The cytoplasm pinches into
two cells.
• A cell plate forms between
the two new nuclei.
• The cell plate gradually
develops into new cell
membranes.
• New cell walls then form
around the cell
membranes.
Animations
• Control of the Cell Cycle
–
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.ht
ml
• How the Cell Cycle Works
–
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cycle_works.h
tml
• Mitosis & Cytokinesis
–
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.htm
l
• Animal Cell Mitosis
–
http://iknow.net/player_window.html?url=media/prophase_video_auto.swf&width=360&heig
ht=285
• Plant Cell Mitosis
–
http://iknow.net/player_window.html?url=media/plant_mitosis_auto.swf&width=360&height
=285
What is the Purpose of
Cell Division?
• When the cell volume/surface increases, then a
cell must divide or split into two, because if it
doesn't then it would literally just be one huge
blob.
• Cell division is necessary for all life, without it
then you would barely exist.
• Cells need to divide because if you lose older cells,
how else would you replace them?
• Your body consists of millions or billions of cells,
and without them you wouldn't be you!