CELL DIVISION
ASEXUAL REPRODUCTION AND
MITOSIS
Cell Division

All cells are derived from

New cells are produced for

This process will differ between
prokaryotes and eukaryotes
Pre-existing cells
growth and to
replace damaged
or old cells

The instructions for making cell parts are
encoded in the DNA, so each new cell
must get a complete set of the DNA
molecules
• DNA must be copied or replicated
before cell division

Each new cells will then have an identical
copy of the DNA
CELL LEVELS OF ORGANIZATION
groups of cells that work
together to perform a specific
function

Tissue-

Organ- group of tissues that perform
a

complex function
Organ system- multiple organs that work
together
CHROMOSOMES
•Chromosomes are found in every
cell of our body.
Chromosomes: rod-like structures
in nucleus that contain hereditary
information (DNA) & appear as
long, thin threads called chromatin
•In order to be alive, we need a full
set of chromosomes = 46. (23 pairs
of chromosomes)
•Each chromosome pairs up with its
partner that looks identical to it (they
both hold the same genes)
Asexual Reproduction
 2 daughter cells produced from a parent
cell

1. BINARY FISSION
Replication of an organism
 Cytoplasm divides equally into two
 Produces a new organism

 Bacteria
 Amoeba
 Paramecium
2. BUDDING
 Mitotic
division of the cytoplasm
 Organism develops a “bud”
 Cytoplasm does NOT divide equally
 Yeast
 Hydra
3. SPORULATION
Spores are produced by the organism
/host

Spores released and grow into new
organism


Bread mold
4. REGENERATION
 Organism
can replace damage cells
OR
 Part of an organism grows into a new
organism
 Lizard
 Starfish
 Planaria
 Lobster
claws
Spiny Brittlestar
Regenerating arm
5. VEGETATIVE PROPAGATION

Occurs in plants

Part of a root, stem or leaves

Grows into a new plant

Bulbs
ASEXUAL
REPRODUCTION
AND MITOSIS
“All cells arise from
preexisting cells” (Virchow)
Karyotypes are images of chromosomes to
display their banding patterns.
A karyotype is a way for scientists to
check chromosomes
NORMAL KARYOTYPE
ABNORMAL KARYOTYPE
Sex
Chromosome
Down
Syndrome
Sister chromatids
Centromere
2 TYPES OF REPRODUCTION




Asexual
1 parent
Offspring are identical
to parent & to each
other
No special organs/cells
Process that divides
cells = mitosis
 In one-celled
organisms = new
organism
 In multi-cellular
organisms = growth
& repair
Sexual




2 parents
Fusion of sperm &
egg nuclei
Offspring have a
combination of traits
from both parents
Process that creates
new cells = meiosis
 Produces sperm &
eggs
MITOSIS
Is the division of the nucleus
 Only occurs in eukaryotes
 Doesn’t occur in some cells such as brain cells

Occurs only in the body cells, known also as
somatic cells
 Results in 2 daughter cells which are identical
to the parent cell AND each other

MITOSIS IN UNICELLULAR

Why is Mitosis important for unicellular
organisms?
 Form
 Every
of reproduction
time an amoeba divides by mitosis a new
identical amoeba is formed!
MITOSIS IN MULTICELLULAR

Cell specialization!
 Separate
roles for each type of cell in the body of a
multi-cellular organism
 Skin
cells, muscle cells, liver cells
THE CELL CYCLE AND MITOSIS

The Cell Cycle: a series of events that cells go
through as they divide
Mitosis
clip..\bi
omovie
s\mitosi
s part
1.mov
Part 2
INTERPHASE
A
period of growth
Occurs
mitosis
 Cell
right before
increases in size
 DNA is copied
 Organelles needed for cell division
are produced
 Then, mitosis (cell division)
occurs with 4 remaining phases:
PROPHASE
•Chromatin condenses to form Chromosomes
•Spindle fibers grow
• Nuclear membrane disappears
•Chromosomes make a
copy of themselves
• Centrioles move to opposite
ends of the cell
Prophase
Cell
Membrane
These are
homologous
pairs of
chromosomes
in the nucleus
METAPHASE- 2ND STAGE
 Meta
= middle
 Chromatids line
up in middle on
“equator”
 Spindle fibers
attach to
centromeres
Metaphase
centrioles
Cell Membrane
Doubled
chromosomes
line up in the
center of the
cell.
ANAPHASE- 3RD STAGE
 “AWAY”
 Doubled
Chromosomes are attached to
spindle fibers
• Chromatids get
ripped apart from
each other
•
Chromatids are pulled
to opposite sides of the
cell
Anaphase
Cell Membrane
TELOPHASE- 4TH STAGE
The cell
membrane
pinches in
 Each new cell is
now in interphase
 New nuclear
membrane forms
 Chromosomes
unwind, pull up &
become chromatin
once again

Telophase
Chromosomes
on opposite
sides of the
cell form 2 new
nuclei.
New Nuclear
membranes!!
Mitosis 2
Cytokinesis
clip
(the Last step!)
• Last Step!!
We’ve got to
divide the rest of
the cell!
• A new cell membrane
forms between the
cells & 2 Daughter
Cells!!!!!
Animal Cell
RESULTS OF MITOSIS:
PROPHASE
ANAPHASE
2 identical cells/ no variety


Mitosis Maintains Chromosome #
INTERPHASE
http://www.cellsalive.com/mitosis.htm
CYTOKINESIS DIFFERENCES IN ANIMAL AND
PLANT CELLS

Animal Cell
 The
cell membrane is drawn inward
 They have centrioles
 Cytoplasm is pinched into 2 equal parts
Plant Cell

Cell plate develops into a separating membrane
RESULTS OF MITOSIS
Chromosome number stays the same from
generation to generation
 2 “daughter cells” produced, each one identical
to “mother cells”
