Decoding Cell Division: The Dance of Life's Continuity Step into the mesmerizing world of cell division with our illuminating SlideShare presentation. From the elegant choreography of mitosis to the intricacies of meiosis, witness the remarkable processes that underpin life's continuity and diversity. In this captivating presentation, we delve deep into the mechanisms of cell division, unraveling the stages and significance of mitosis and meiosis. Explore how cells meticulously replicate their DNA, segregate their chromosomes, and orchestrate their division to ensure the transmission of genetic information with precision and fidelity. Through vivid illustrations, clear explanations, and real-world examples, we illuminate the significance of cell division in growth, development, and reproduction. Gain a newfound understanding of how errors in cell division can lead to diseases like cancer and genetic disorders, and learn about the cutting-edge research driving advancements in this field. Whether you're a student, educator, or enthusiast of life sciences, our presentation offers valuable insights into one of the most fundamental processes of life. Join us as we unravel the mysteries of cell division and marvel at the beauty and complexity of nature's continuity. Don't miss this opportunity to deepen your knowledge and appreciation of cell biology. Embark on a journey into the heart of cell division and discover the dance of life's continuity unfolding before your eyes.

1. Cell Division
Cell Reproduction
Cell Cycle
Mitosis & Meiosis
MR. SAGAR PANDYA
ASSISTANT PROFESSOR
M.Sc. Nursing (Child Health Nursing)
Bhagyalaxmi College Of Nursing, Modasa (Guj.)

2. THE CELL CYCLE /CELL DIVISION /CELL
REPRODUCTION
•The CELL CYCLE is an ordered sequence of events in
which a body cell duplicates its contents and divides in two
new cell (daughter cells).
•The CELL CYCLE is the period between two cell division.
•Also known as cell division or cell reproduction.
•Three types of cell division, or cell reproduction
Prokaryotes (bacteria)
Binary fission divides forming two new identical
cells
Eukaryotes
oMitosis
-Cell or organism growth.
-Replacement or repair of damaged cells.
oMeiosis

3. Why do cells divide?
1: DNA Overload
◦ If cells grow without limit, an “information
crisis” would develop
◦ DNA cannot serve the needs of the increasing
size of cell
2: Exchange of materials
◦ Food and oxygen have to cross membrane
very quickly
◦ Waste must get out
◦ If cell is too large, this occurs too slowly and
cell will die.
3: For growth , repair & reproduction.

4. PROKARYOTIC CELL DIVISION
 Binary fission
◦ 3 main steps:
1: DNA Replication—DNA is copied, resulting in 2
identical chromosomes.
2: Chromosome Segregation—2 chromosomes separate,
move towards ends (poles) of cell.
3: Cytokinesis—cytoplasm divides, forming 2 cells.
◦ Each new daughter cell is
genetically identical to parent cell.
•Prokaryotes have no nucleus.
•They have a single circular chromosome.
•Prokaryotes simply divide their cells in two by binary
fission.

5. Eukaryotes Cell Division
 Eukaryotes must divide their nucleus
(and other organelles such as
mitochondria) in preparation for cell
division (mitosis or meiosis)
 Before the nucleus divides the genetic
material replicates (duplicates)
 Cell cycle has two parts:
◦ Growth and preparation (Interphase)
◦ Cell division (M Phase- Mitosis or
Meiosis)
 Nuclear division (Mitosis/Karyokinesis)
 Cytokinesis (Cytoplasm division)

6. INTERPHASE
 INTERPHASE: Period of growth and DNA replication
between cell divisions.
 Three phases:
◦ G1 Phase (First Gap Phase):
 Cell increases in size and volume.
 Cell metabolically active.
 Duplicates organelles and cytosolic components.
 Centrosome replication begins.
◦ S Phase (Synthesis of DNA):
 Replication of chromosomes (DNA replication /
duplication).
◦ G2 Phase (Second Gap Phase):
 Organelles double.
 New cytoplasm forms.
 Cell growth continues (Enzymes and proteins are
synthesized).
 Centrosome replication completed.

8. Terminology
 Chromatin Material-
Thin threadlike fibrous form of DNA and
proteins in nucleus (uncondensed
chromosomes).
 Chromatid-
Single condensed chromosome
(condensed chromosome).
 Sister chromatids-
Identical structure of homologus
condensed chromosome.
 Centromere –
Point where sister chromatid
/ two chromatids are joined together.

9. • Kinetochore-
At the outside of each centromere is
a protein complex (attachment site for
mitotic spindle).
• Diploid-
Two sets of chromosomes (2n),in humans 23
pairs or 46 total.
• Haploid-
One set of chromosome (n),in humans 23
chromosomes (Gametes or sex chromosome).
• Homologous pair-
Each chromosome in pair are identical (Carry
genes from same trait).
only one pair is different- sex chromosome (X or
Y)

10. • Tetrad-
Four chromatids (2 homologous
sister chromatid pairs) form
a structure during meiosis.
• Synapsis -
Synapsis (also called syndesis) is the pairing of two
homologous chromosomes that occurs during meiosis.
• Crossing-over -
The exchange of genetic material between homologous
chromosomes (In prophase-I of meiosis).
•Genetic recombination –
It is result of Crossing-over - that is, the formation of new
combinations of genes.

12. MITOSIS
(SOMATIC CELL DIVISION)
•The process of cell division which results in the
production of two daughter cells from a single
parent cell.
•The daughter cells are identical to one another
and to the original parent cell.
•Process that divides cell nucleus to produce two
new nuclei each with a complete set of
chromosomes.
•Mitosis is the basis of asexual reproduction.

13. Mitosis complete
by two process-
1) NUCLEAR DIVISION (KARYOKINESIS)
4 sub-phases:
1st – Prophase
2nd – Metaphase
3rd – Anaphase
4th – Telophase
followed by:
2) CYTOPLASMIC DIVISION (CYTOKINESIS)
Interphase
Cytokinesis
Nuclear division

14. 1) NUCLEAR DIVISION
(KARYOKINESIS)
 Nuclear division is most important part of
eukaryotic cell division.
 In Mitosis ,as noted earlier, is the
distribution of two sets of chromosomes
into two separate nuclei equally.
 Biologists divide the process into four
phases: Prophase, Metaphase,
Anaphase, Telophase.

15. •Chromosome condense or visible (Chromatin
materials/fibers to chromatids to sister chromatid
pair).
•Two homologous chromatids attached at a
constricted region called a centromere (holds the
chromatid pair together).
•Centrioles migrate to the poles (only in animals).
•Microtubules form (Mitotic spindle/Spindle fiber)
from centrioles.
Prophase

16. •At the outside of each centromere is a protein
complex known as kinetochore.
•Microtubules attach to the kinetochore for the
pulling and pushing of chromosomes.
•The nuclear envelope breaks down or starts
disappear.

17. Metaphase
 Chromosomes line up at the center of the cell through
the pulling pushing movement of mitotic spindle
(Microtubules).
 The centomeres of the chromatids pairs at the exact
center of the mitotic spindle.
 This midpoint makes a imaginary line called
metaphase plate.

18. • Centromeres split out (Sister chromatids
sreparate).
• Spindle fibers pull one set of chromosomes
(chromatids) to each pole.
• Free spindle fibers lengthen and push poles of
cell apart.
Anaphase

19. Telophase
• The final stage of mitosis.
• Chromosomes uncoil (chromatids to chromatin material).
• Spindle fibers disappears.
• Nuclear envelopes form around both groups of
chromosomes.
• Cytokinesis occurs, enclosing each daughter nucleus into
a separate cell.
• Cleavage furrow forms on plasma
membrane ( A constricted ring at
the center of plasma membrane
due to actin protein).

20. 2) CYTOPLASMIC DIVISION
(CYTOKINESIS)
 Occurs at end of Mitosis.
 Cytokinesis through the formation of
cleavage furrow (A ring of microtubules
contract , pinching the cell in half).
Division of the cytoplasm to form 2 new
daughter cells.
 Organelles are divided.
Daughter cells are genetically identical.

21. Cytokinesis
Cleavage
furrow
Contracting ring of
microfilaments
Daughter
cells
Cleavage
furrow
Cells return to interphase

23. MeIOSIS
(REPRODUCTIVE CELL DIVISION /GERMCELL
DIVISION)
•Meiosis is the type of cell division by which germ
cells (eggs and sperm) are produced.
•One parent cell produces four daughter cells.
•Daughter cells have half the number of chromosomes
found in the original parent cell.
•Meiosis shuffles genes in new combinations.
A division of the nucleus/cell that reduces chromosome
number by half (forms four haploid cells from a diploid cell)

24. •Meiosis results in genetically different cells.
•Meiosis and fertilization are the basis of sexual reproduction.
•During meiosis, DNA replicates once, but the nucleus divides
twice.
•Completed in two stages- Meiosis-I or Meiosis-II.
•Four sub-phases described for each stages.

25. Meiosis complete in two stages-
1) MEIOSIS-I
A) NUCLEAR DIVISION
(KARYOKINESIS)
4 sub-phases:
Prophase-I
Metaphase-I
Anaphase-I
Telophase-I
followed by:
B) CYTOPLASMIC
DIVISION-I
(CYTOKINESIS-I)
Followed by:
2) MEIOSIS-II
A) NUCLEAR DIVISION
(KARYOKINESIS)
4 sub-phases:
Prophase-II
Metaphase-II
Anaphase-II
Telophase-II
followed by:
B) CYTOPLASMIC DIVISION-II
(CYTOKINESIS-II)

27.  Sex cells divide to produce GAMETES (sperm or egg).
 Gametes have HALF the numbers of chromosomes.
 Occurs only in GONADS (testes or ovaries).
 Male: SPERMATOGENESIS – Formation of
sperm.
 Female: OOGENESIS – Formation of egg or
ova/ovum
 Heredity : Way of transferring the genetic information to
offspring.
 Chromosome theory of heredity: “Chromosomes
carry genes”.
 Gene : Unit of heredity.

28. Spermatogenesis
2n=46
Human
sex cell
Diploid (2n)
n=23
n=23
meiosis I
n=23
n=23
n=23
n=23
sperm
haploid (n)
meiosis II
4 sperm cells are
produced from each
primary spermatocyte.
Primary Spermatocyte
Secondary Spermatocyte
Secondary Spermatocyte

29. Oogenesis
2n=46
Human
sex cell
Diploid (2n)
n=23
n=23
Meiosis I
n=23
egg
Haploid
(n)
Meiosis II
29
Polar
Bodies
(die)
*** The polar bodies die… only one ovum
(egg) is produced from each primary oocyte.
Primary oocyte
Secondary oocyte
Ova
***One ova or three polar
bodies produce from each
primary oocyte

31. MEIOSIS-I
(Homologous
chromosomes
separate)
31

32. 1) MEIOSIS-I
A) NUCLEAR DIVISION (KARYOKINESIS)
Prophase-I
 Longest and most complex phase
 90% of the meiotic process is spent in prophase-I.
 Chromosomes condense.
 Nuclear envelop & nucleolus disappears.
 Centromeres moves to opposite poles.
 Synapsis occurs: Homologous chromosomes come together to
form a tetrad.
 Tetrad is two chromosomes or four chromatids (sister and
nonsister chromatids).
 Crossing over (variation) may occur between non sister
chromatids at the chiasmata.
 Crossing over: Segment of non sister chromatids break and
reattach to the other chromatid.
 Chiasmata (Chiasma): The site of crossing over.

33. Prophase I - Synapsis
Homologous chromosomes
sister chromatids sister chromatids
Tetrad

34. Homologous Chromosomes
 Pair of chromosomes (maternal and paternal) that
are similar in shape and size.
 Homologous pairs (tetrads) carry genes controlling
the same inherited traits.
 Each locus (position of a gene) is in the same
position on homologues.
 Humans have 23 pairs of homologous
chromosomes.
a. 22 pairs of autosomes
b. 01 pair of sex chromosomes

35. Crossing Over
Creates variation (diversity) in the offspring’s traits.
Nonsister chromatids
Chiasmata: site
of crossing over
Variation
(Genetic
recombination)
Tetrad

36. Prophase I

37. Metaphase-I
Shortest phase
Tetrads or homologous
chromosomes move to
center of cell.
Tetrads align on the
metaphase plate.
Metaphase plate

39. Anaphase-I
• Microtubules of spindle shorten.
•Homologous chromosomes separate and move
towards the poles.
•Sister chromatids remain attached at their
centromeres.
Sister chromatids
remain attached
Homologous
chromosomes
separate

40. Telophase-I
 Each poles now has haploid (n) set of
chromosome.
 Nuclear envelopes form around each set of
chromosomes.
 Two daughter nuclei formed.
 Each new nucleus is now haploid.
 Sister chromatids are no longer identical because
of crossing over.
 Sister chromatids uncoiled.
 Cytokinesis occurs and two haploid daughter cells

41. Telophase I & Cytokinesis I

42. B) CYTOPLASMIC DIVISION-I
(CYTOKINESIS-I)
 Occurs at end of Meiosis-I.
 Cytokinesis through the formation of cleavage furrow
(A ring of microtubules contract , pinching the cell in half).
Constricted ring forms due to activation of actins protein
present in plasma membrane.
 Division of the cytoplasm to form 2 new daughter cells.
 Organelles are divided.
Daughter cells (haploid) are genetically different from
parent cell.
Undergo further division continue in meiosis-II.

43. Cytokinesis
Cleavage
furrow
Contracting ring of
microfilaments
Daughter
cells
Cleavage
furrow Undergo further division
continue in meiosis-II.

44. MEIOSIS-II
(Sister
Chromatids
Separate)
44

45. 2) MEIOSIS-II
Daughter cells undergo a second
division of meiosis is meiosis-II.
No interphase-II.
Very short stage.
No DNA replication.
Meiosis-II is similar to mitosis.
In meiosis-II 4 haploid cells forms
from 2 haploid cells (daughter cells)
formed in meiosis-I.
Meiosis-II also complete in two
processes:
A)Nuclear division (Karyokinesis)
B)Cytoplasmic division-II
(Cytokinesis –II)
Meiosis II
Meiosis -I

46. Prophase-II
A) NUCLEAR DIVISION
(KARYOKINESIS)
Same as Prophase in mitosis:
*Nucleus & nucleolus disappear
*Chromosomes condense
*Chromatids makes sister chromatid (attached
at
centromere)
*Centriole moves to opposite poles
*Spindle forms
*Spindle attached to sister chromatids (through
kinatochore)

47. Prophase II

48. Metaphase-II
 Sister chromatids move
to the center.
 Chromosomes (not
homologous) line up at
equator.
 Forms metaphase plate.

49. Anaphase-II
Same as Anaphase in
mitosis.
Centromeres divide and
sister chromatids migrate
separately to each pole.
 Individual chromosomes are
pulled to poles.
 Microtubules of spindle
shorten.

50. Telophase-II
 Same as telophase in mitosis.
 The final stage of meiosis.
 Cell division is complete. Four haploid daughter cells are obtained.
Chromosomes uncoil (chromatids to chromatin material).
 Spindle fibers disappears.
 Nuclear envelopes form around four groups of chromosomes.
 Nuclei and Nucleoli reforms.
 FOUR HAPLOID DAUGHTER cells are produced Called GAMETES
(eggs and sperm)
 Cytokinesis occurs, enclosing each daughter nucleus into a separate
cell.
 Cleavage furrow forms on plasma membrane ( A constricted ring at
the center of plasma membrane due to actins protein).

51. Telophase II & Cytokinesis II

52. B) CYTOPLASMIC DIVISION-II
(CYTOKINESIS-II)
 Occurs at end of Meiosis-II or meiosis.
 Cytokinesis through the formation of cleavage furrow (A ring of
microtubules contract , pinching the cell in half).
Constricted ring forms due to activation of actins protein present in
plasma membrane.
 Division of the cytoplasm to forms 4 new daughter cells from both
haploid cells.
 Organelles are divided.
Daughter cells (haploid) are genetically different from parent cell.
Meiosis division is completed.

53. Centrosomes
(with centriole
pairs) Centrioles
Sites of crossing over
Spindle
Tetrad
Nuclear
envelope Chromatin Sister
chromatids Fragments
of the
nuclear
envelope
Centromere
(with a
kinetochore)
Spindle microtubules
attached to a kinetochore
Metaphase
plate
Homologous
chromosomes
separate
Sister chromatids
remain attached
Chromosomes duplicate Prophase I Metaphase I Anaphase I
INTERPHASE: MEIOSIS I: Homologous chromosomes separate

54. Prophase II Metaphase II Anaphase II
MEIOSIS II: Sister chromatids separate
Sister chromatids
separate
Haploid daughter
cells forming
Telophase II
and Cytokinesis II