Mitosis is the process of cell division that results in two daughter cells having the same number and type of chromosomes as the parent nucleus. It produces genetically identical cells in both animals and plants. The main stages of mitosis are prophase, prometaphase, metaphase, anaphase and telophase. During prophase, the chromatin condenses into chromosomes. In metaphase, the chromosomes align along the metaphase plate. In anaphase, the sister chromatids are separated and moved toward opposite poles. Telophase involves the reformation of the nuclei around the separated chromosomes. Cytokinesis then divides the cytoplasm, completing cell division.

1. 1
Lecture on “Mitosis”
By
• Dasari Sreekanth. M.Sc., NET, TS/AP-SET, GATE, (Ph.D.)
Research scholar,
Department of Botany,
Osmania university,
Email: Shreekanthdasari@gmail.com

2. 2
Cell Division
• An integral part of the cell cycle
• Production of genetically identical daughter cells
• Cells duplicate their genetic material
– Before they divide, ensuring that each daughter
cell receives an exact copy of the genetic
material, DNA

3. 3
DNA
• Genetic information - genome
• Packaged into chromosomes
50 µm
Figure 12.3

4. 4
• Because of duplication, each condensed chromosome
consists of 2 identical chromatids joined by a centromere.
• Each duplicated chromosome contains 2 identical DNA
molecules (unless a mutation occurred), one in each
chromatid:
Chromosome Duplication
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Two unduplicated
chromosomes
Centromere
Sister
chromatids
Sister
chromatids
Duplication
Non-sister
chromatids
Two duplicated chromosomes

5. 5
Chromosome Duplication
0.5 µm
Chromosome
duplication
(including DNA
synthesis)
Centromere
Separation
of sister
chromatids
Sister
chromatids
Centrometers Sister chromatids
A eukaryotic cell has multiple
chromosomes, one of which is
represented here. Before
duplication, each chromosome
has a single DNA molecule.
Once duplicated, a chromosome
consists of two sister chromatids
connected at the centromere. Each
chromatid contains a copy of the
DNA molecule.
Mechanical processes separate
the sister chromatids into two
chromosomes and distribute
them to two daughter cells.
• In preparation for cell division, DNA is replicated and the chromosomes condense
• Each duplicated chromosome has two sister chromatids, which separate during cell
division

6. 6
chromatin
duplicated
chromosome

7. 7
Have your bodyHave your body
changed in thechanged in the
pass sixpass six
months?months?
Tall/WeightTall/Weight

8. 8
Are you taller?Are you taller?

9. 9
Broken a boneBroken a bone
recently?recently?

10. 10
Wound – how doesWound – how does
your body repairyour body repair
itself?itself?

11. 11
Mitosis

Mitosis term derived from greek word
‘Mitos’ means thread or fibril.

Parent cell produces two daughter cells.

two identical daughter cells that
are genetically identical to the
parent cells.

12. 12
Mitosis

First observed by ‘Straasburger’ in plant
cell (1870).

Boveri and Flemming observed in Animal
cell.

Term ‘mitosis’ given by- Flemming in
1882.

Called also Equational division- due to
equal distribution of chromosomes in
daughter nuclei.

Also called as Somatic cell division.

13. 13
Q: What kind of cells would
perform mitosis?
A: Somatic cells
(all body cells except gamete cells)

14. 14
Mitosis

The sites of mitosis in plants is –
meristematic regions.

Root apex

Shoot apex

Intercalary meristem

Lateral meristem

Leaves

Embryo

Seeds.
Intestinal Cell
embryoEpithelial Cell

15. 15
Mitosis

In animals;

Embryo

Skin, bone marrow.

16. 16
Mitosis

Some haploid & diploid cells divide by mitosis.

Each new cell receives one copy of every
chromosome that was present in the original cell.

Produces 2 new cells that are both genetically
identical to the original cell.
DNA duplication
during interphase
Mitosis
Diploid Cell

17. 17
Phases of Mitosis

18. 18
Mitosis
The Basic Phases of a
Cell’s Life:
I. Karyokinesis.
II. Cytokinesis

19. 19
Karyokinesis

Nuclear division of parent cell known
as karyokinesis.

In greek;

Karyon= nucleus,

kinesis-= movement.

Karyokinesis divided into 4 phases;
• Prophase
• Metaphase
• Anaphase
•

20. 20
Prophase
PROPHASE
Early mitotic
spindle
Aster
Centromere
Chromosome, consisting
of two sister chromatids
Prophase can be
devided into
Early prophase
Mid prophase
Late prophase.

21. 21
Prophase

Early Prophase:

DNA molecules condensed
and forms short
chromosomes.

In this stage chromosomes
appear like a ball of wool,
so called spireme stage.

In animal cells
Centriosome (centriole)
divided into two and moves
towards opposite pole.
PROPHASE
Early mitotic
spindle
Aster
Centromere
Chromosome, consisting
of two sister chromatids

22. 22
The Mitotic Spindle apparatus.

Also called achromatic figure.

Centrioles + aster + spindle fibers = Mototic
spindle apparatus.
• The apparatus of microtubules controls
chromosome movement during mitosis
• The centrosome replicates, forming two
centrosomes that migrate to opposite ends of the
cell
• Assembly of spindle microtubules begins in the
centrosome, the microtubule organizing center
• An aster (a radial array of short microtubules)
extends from each centrosome.

23. 23
Early Prophase:
PROPHASE
Early mitotic
spindle
Aster
Centromere
Chromosome, consisting
of two sister chromatids
Centrioles produces
out fine microtubular
fibrils called Aster rays.
Plants cells do not
contain centrioles so
called Acentric mitosis.
Animals – centric
mitosis.

24. 24
Mid Prophase:
PROPHASE
Early mitotic
spindle
Aster
Centromere
Chromosome, consisting
of two sister chromatids
Chromosomes shift
towards the periphery
and leave a clear area.
It becomes shorter
and thicker.
Each chromosome
consists of two
longitudinal threads
called chromatids.

25. 25
Late Prophase:
PROPHASE
Early mitotic
spindle
Aster
Centromere
Chromosome, consisting
of two sister chromatids
Spindle fibers start
appearing around the nucleus.
Size of chromosomes is
much reduced.
Spindle poles are formed
without asters in plants
(anastral mitosis).
With asters in
animals( astral mitosis).

26. 26
Metaphase
 Metaphase is the longest
stage of mitosis, lasting
about 20 minutes.
 The centrosomes are
now at opposite ends of the
cell.
The chromosomes
arranged on the metaphase
plate= congression.
• The chromosomes’
centromeres lie on the
metaphase plate.
METAPHASE
Spindle
Metaphase
plate
Centrosome at
one spindle pole

27. 27
Metaphase
For each chromosome, the
kinetochores of the sister
chromatids are attached to
kinetochore microtubules coming
from opposite poles.
 The entire apparatus of
microtubules is called the spindle
because of its shape.
This phase is useful for study of
chromosomes morphology.
METAPHASE
Spindle
Metaphase
plate
Centrosome at
one spindle pole

28. 28
The Mitotic Spindle apparatus.

Also called achromatic figure.

Centrioles + aster + spindle fibers = Mototic
spindle apparatus.
• The apparatus of microtubules controls
chromosome movement during mitosis
• The centrosome replicates, forming two
centrosomes that migrate to opposite ends of the
cell
• Assembly of spindle microtubules begins in the
centrosome, the microtubule organizing center
• An aster (a radial array of short microtubules)
extends from each centrosome.

29. 29
• Some spindle microtubules attach to the kinetochores of
chromosomes called= discontinuous micro tubules./
kinetochore micro tubules.
• Some spindle microtubules are not attached to kinetochore
called= non kinetochore microtubules or continuous
microtubules.
In anaphase, sister chromatids separate and move along the
kinetochore microtubules toward opposite ends of the cellMicrotubules Chromosomes
Sister
chromatids
Aster
Centrosome
Metaphase
plate
Kineto-
chores
Kinetochore
microtubules
0.5 µm
Overlapping
nonkinetochore
microtubules
1 µmCentrosome
The Mitotic Spindle

30. 30
Anaphase
 Anaphase is the shortest
stage of mitosis.
 the centromeres of
chromosomes start divide into
two.
 two daughter chromatids are
separated.
 daughter chromatids are
migrate towards opposite
poles.
Spindle fibers are attached to
the centromere and pull the
chromosomes to the poles.
ANAPHASE
Daughter
chromosomes

31. 31
ANAPHASE
Daughter
chromosomes
Anaphase
as their kinetchore
microtubules (Discontinuous
microtubules ) shorten.
Because these microtubules
are attached at the centromere
region, the chromosomes move
centromere first (at about 1
µm/min).
 The cell elongates as the
nonkinetochore microtubules
lengthen.
By the end of anaphase, two
groups of chromosomes are
formed, one at each pole.

32. 32
ANAPHASE
Daughter
chromosomes
Anaphase
Anaphasic chromosomes
appear as V,L,J,I shaped.
Type of
chromosome
Shape Centromere
position.
Metacentric V Median
Submetacentric L Submedian
Acrocentric J Sub-terminal
Telocentric I Terminal.

33. 33
Telophase
Viscocity of cytoplasm
decreases.
Nuclear envelope is formed
around each set of chromosomes.
Chromosomes form chromatin.
 nucleolus is reformed.
Spindle apparatus disappear.
• Mitosis, the division of one
nucleus into two genetically
identical nuclei, is now
complete.
•This phase is just reverse of
prophase.
TELOPHASE AND CYTOKINESIS
Nucleolus
forming
Cleavage
furrow
Nuclear
envelope
forming

34. 34
Mitosis in a plant cell
1 Prophase.
The chromatin
is condensing.
The nucleolus is
beginning to
disappear.
Although not
yet visible
in the micrograph,
the mitotic spindle is
staring to from.
Prometaphase.
We now see discrete
chromosomes; each
consists of two
identical sister
chromatids. Later
in prometaphase, the
nuclear envelop will
fragment.
Metaphase. The
spindle is complete,
and the chromosomes,
attached to microtubules
at their kinetochores,
are all at the metaphase
plate.
Anaphase. The
chromatids of each
chromosome have
separated, and the
daughter chromosomes
are moving to the ends
of cell as their
kinetochore
microtubles shorten.
Telophase. Daughter
nuclei are forming.
Meanwhile, cytokinesis
has started: The cell
plate, which will
divided the cytoplasm
in two, is growing
toward the perimeter
of the parent cell.
2 3 4 5
Nucleus
Nucleolus
ChromosomeChromatine
condensing

35. 35
Cytokinesis in animal cell

Cleavage of cell into two
halves.

In middle region of cell,
microfilaments induces
the cell membrane to
invaginate.

The furrow forms and
deepens centripetally
and finally cleaves the
parent cell into two
daughter cells.

This method is called
cleavage method.

36. 36
Cytokinesis In Animal And Plant Cells
Daughter cells
Cleavage furrow
Contractile ring of
microfilaments
Daughter cells
100 µm
1 µmVesicles
forming
cell plate
Wall of
patent cell Cell plate
New cell wall
(a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (SEM)

37. 37
ANIMAL VS. PLANT MITOSIS

ANIMAL CELL

Centriole and
aster present

Daughter cells
separated by
cleavage furrow

PLANT CELL

No visible
centriole or aster

Daughter cells
separated by cell
plate

38. 3838
Cell Cycle

39. 39
Phase
Chromosome
Appearance & Location
Important Events
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
DNA replication, cell
grows and replicates
organelles
Nuclear envelope
disappears, spindle fibers
form
DNA copies itself;
chromatin
Chromosomes coil up
Chromosomes line up in
the middle
Spindle fibers connect to
chromosomes
Chromosome copies divide
and move apart
Spindle fibers pull
chromosome copies apart
to opposite poles
Chromosomes uncoil back
into chromatin
Nuclear envelopes reform,
2 new nuclei are formed,
spindle fibers disappear
Division of the rest of the
cell: cytoplasm and
organelles
Chromatin

40. 40
Mitosis Application

41. 41
Functions of Cell Division
20 µm100 µm 200 µm
(a) Reproduction. An amoeba,
a single-celled eukaryote, is
dividing into two cells. Each
new cell will be an individual
organism (LM).
(b) Growth and development.
This micrograph shows a
sand dollar embryo shortly after
the fertilized egg divided, forming
two cells (LM).
(c) Tissue renewal. These dividing
bone marrow cells (arrow) will
give rise to new blood cells (LM).

42. 42
Why Is Cell Division Important?
1. All Living Things are made of Cells

43. 43
How do little elephants grow up to be BIG
elephants?

44. 44
The process of asexual
reproduction begins after a
sperm fertilizes an egg.

45. 45
1. Growth
2. Repair
3. Replacement

46. 46
CLONING
• The process to produce genetically identical cells /
tissues / organisms / population from the mitosis of a
single parent cell (clone)
• Naturally: asexual reproduction, vegetative
propagation (plant)
• Artificially: cloning (animal), tissue culture (plant)
Why?
–Increase quantity
–Improve quality
–Ensure uniformity of traits

47. 47
Controlled Mitosis
• The ability of cell to divide at its own timing and rate
• Enables __normal_________ growth and development
and maintenance for perpetuity of living things

48. 48
Uncontrolled Mitosis
• If the genes that regulate the cell cycle are damaged or
mutated, cell divide __abnormal___cell growth_____
• Cause:
– Harmful ray: nuclear radiation, UV ray
– Viruses
– Carcinogenic chemicals: food additives, benzo (α)
pyrene in cigarette smoke

49. 49
The Effects of Uncontrolled Mitosis
• Unregulated and very fast
division increase the number
of abnormal cells
• Form an abnormal mass –
tumour
• Types of tumour:
– Malignant
• Invasive by metastasis
• Cancer
– Benign
• Localize
• Does not cause serious
problems
• Remove by
___________
What is the treatment ofWhat is the treatment of
cancer?cancer?
BrainBrain
cancercancer
BreastBreast
cancercancer