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Cellular Reproduction - Mitosis
MITOSIS = Cell division
When parent cell forms two identical daughter cells
Daughters!
Momma!
Momma!
Why do cells divide?
Multicellular organisms:
1) Growth
2) Maintenance/repair
of tissues (ex: blood
cells)
Unicellular organisms:
Asexual reproduction
Cell division involves:
Replication of DNA –
copying the genetic material
Distribution of DNA –
dividing the genetic material
evenly between two cells
Cytokinesis –
dividing the cytoplasm between
two cells
Normally, DNAChromosome
in the nucleus is called CHROMATIN.
Just before
cell division,
It is seen
as a thin thread loosely wrapped around
DNA coils
tightlylike
intoaabeaded necklace.
proteins
chromosome. The
chromosome is very
compact and can be seen
DNA is a double helix
with a light microscope
When stretched out, it can
Chromatin be as long as 2 meters
DNA double helix
proteins
Replication: Copying the DNA
Occurs before the DNA condenses
(S phase of interphase)
The original and its
identical copy are
called sister
chromatids.
Sister chromatids
are attached to
each other by a
centromere.
During mitosis, the sister chromatids will be separated so
each cell has the complete DNA information
A chromosome is made up of two identical halves
called chromatids.
The Cell Cycle
Time from the
formation of a
cell until it
divides
The Cell Cycle
Two major
phases:
Interphase
Most cell
activities
occur
Growth
Making
proteins
Performing
specialized
functions
The Cell Cycle
Two major
phases:
Mitosis
Cell division
Cycle time
varies:
Embryonic
cells complete
the cycle in
hours
Stem cells are
in interphase
for 20 hours
Nerve cells
remain in
interphase
G1 phase of interphase – growth, duplication of
organelles, making proteins.
S-phase of interphase: DNA replication
G2 phase: duplication of centrosome
Stages of Mitosis
Prophase : centrosomes separate and spindle
forms; chromosomes are condensing
ProMetaphase : break down of nuclear envelope;
centrosomes arrive at two opposite poles;
spindles attach to chromosomes
Metaphase : chromosomes move to the equator
Anaphase : sister chromatids separate (become
daughter chromosomes)
Telophase : spindle disappears; nuclear envelope
forms, DNA unfolds
cytokinesis: cytoplasm divides
Two daughter cells are now complete
Cytokinesis
Division of the
Cytoplasm
Animal cells:
cleavage furrow
forms
Cell pinches in
towards the
center
Cytokinesis
Plant cells: cell plate forms
New cell walls and
membranes form
from the cell plate
SUMMARY: What happens to
chromosomes prior/during mitosis?
1) chromosomes replicate
**interphase
2) chromosomes coil
**prophase
3) chromosomes align
**metaphase
4) sister chromatids separate **anaphase
5) chromosomes uncoil
**telophase
Animal Prophase
Plant
Animal
Metaphase
Animal Anaphase
Animal Telophase
The Cell Cycle and Cancer
Cancer results
from uncontrolled
cell division.
A cancerous
growth is called a
tumor.
In Cancer, often one of the checkpoints that
regulate mitosis don’t work
The Cell Cycle and Cancer
Cancer cells
Lack differentiation
Have abnormal
nuclei
Undergo metastasis
Cancer treatment:
• Radiotherapy
• Chemotherapy
• Hormonal therapy
Cancer prevention:
• Consumption of foods rich in vitamins A and C
(dark green leafy vegetables, carrots, fruits)
• Avoid salted, pickled or smoked food.
• Consumption of vegetables from the cabbage
family.
Learning objectives
1. Cellular reproduction is an important process for
growth and development as well as repair of tissues in
multicellular organisms.
2. The cell cycle is composed of a number of phases
where specific events occur (interphase and mitosis are
the two major phases).
3. Mitosis is divided into four phases: prophase,
metaphase, anaphase and telophase, which is followed
by cytokinesis
4. Cancer is caused by uncontrolled cell division