The document provides an overview of mitosis and meiosis. It describes the cell cycle and its two main phases: interphase and M-phase. Interphase consists of G1, S, and G2 phases where the cell grows and prepares for division. M-phase involves either mitosis or meiosis. Mitosis divides somatic cells and results in two identical daughter cells. Meiosis produces gametes through two cell divisions, resulting in four daughter cells each with half the number of chromosomes. The stages of each process including prophase, metaphase, anaphase and telophase are defined in detail.

1. MITOSIS AND MEIOSIS
PRESENTED BY – SMRUTI RANJAN MASANTA
M.PHARM(1ST YR)
PHARMACOLOGY

2. CONTENT
 Cell cycle
 Interphase
 M-phase
 Mitosis
• Prophase
• Prometaphase
• Metaphase
• Anaphase
• Telophase
 Meiosis
• Meiosis-I
• Meiosis-II

3. Cell cycle
 It is a sequence of events which occurs between the
formation of cell and its division in to daughter cells.
 It consist of 2 phases
 Interphase
 M-phase

4. Interphase
 Cell spends majority of time in this phase for
preparation for cell division. Its metabolically most
active stage.
 G1 phase: In which cell grows and function normally,
Protein synthesis, ATP synthesis, Raw material for DNA
synthesis occur.
 S phase: In which DNA replication occur. The DNA
content of chromosome is now doubled and cell
proceed to mitosis.
 G2 phase: In which cell resumes its growth, protein for
spindle fibres synthesized and organelles like centrioles,
mitochondria, chloroplast are also doubled.

5. M-phase
 In this phase cell division takes place. Generally of two
type.
 Karyokinesis
 Mitosis
 Meiosis
 Cytokinesis

6. Mitosis(Equational division)
 It is a process by which a cell divides into two daughter cells
each having exactly identical number of chromosomes to
that of parent cell.
 It generally occurs in somatic (vegetative cells) cells.
 This type of division was termed as mitosis by W.
Flemming (1882).
 Stages of mitosis:
 Prophase
 Prometaphase
 Metaphase
 Anaphase
 Telophase
 cytokinesis

7.  (A to H) Fluorescence micrographs
of mitosis in fixed newt lung cells
stained with antibodies to reveal the
microtubules (green), and with a
dye (Hoechst 33342) to reveal the
chromosomes (blue). The spindle
forms as the separating astral MT
arrays, associated with each
centrosome (A to C), interact with
the chromosomes. Once the
chromosomes are segregated into
daughter nuclei (F and G), new MT-
based structures known as stem-
bodies form between the new nuclei
(G). These play a role in cytokinesis
(H).

8. Prophase
 It is the longest phase of
mitosis.
 In which chromatin
condenses into chromosome
and then thicken and shows
two distinct chromatids
which connected by
centromere.
 Centriole divide and begins
to move to opposite side of
the cell.
 Spindle fibres begins to form.
It consist of microtubules and
proteins called tubulin.

9. Prometaphase
 The disappearance of
nuclear membrane and
nucleolus marks the
beginning of this stage.
The distinction between
cytoplasm and
nucleoplasm is lost. It is
called extra-nuclear
mitosis or eumitosis.
 The chromosomes get
attached to spindle fibres
by their centromeres and
started to move towards
equator.

10. Metaphase
 At metaphase the
chromosomes have
reached the central
equatorial portion of the
spindles. They are aline to
form the equatorial
plate/metaphasic plate.
 Chromosomal spindle
fibres are attached to the
kinetochore/centromere of
chromosome.
 The continuous fibres
extends from pole to pole.

11. Anaphase
 Chromosomes break at
centromeres and the sister
chromatids move to opposite
side of the cell. Interzonal
fibres form due to break
down of centromere.
 The number of chromosomes
doubles.
 The shape of chromosomes is
identified, that appear like
letters
K(metacentric),L(submetace
ntric),j(acrocentric),i(telocen
tric).

12. Telophase
 The chromosomes reach
the opposite pole.
 Chromosomes
decondensed to form
chromatin, nuclear
membrane reappears.
 The spindle fibres
disassemble and
disappear.
 Cleavage furrow appears.

13. Cytokinesis
 In animal cell, the cleavage
furrow becomes deeper as
spindle breakdown and
finally join to form two
daughter cells.
 In plant cell, the cell plate
is formed to separate the
two daughter cells. It
begins at the Centre of the
cell and proceeds towards
the periphery.

14. Significance of mitosis
 It helps in growth.
 It helps in repair and regeneration.
 It helps in maintaining genetic stability.
 It helps in asexual reproduction in lower organisms.

15. Control of mitosis and mitotic poisons
 Cell area to volume ratio.
 Nucleocytoplasmic ratio(nuclear mass: cytoplasm).
 Mitogens are some substance stimulate mitotic
division
e.g.- cyclins, auxins, gibberellin, insulin, cytokinin.
 Mitotic poison are substance that inhibit mitosis.
e.g.- cyanide-stops division in prophase.
colchicine-stops division in metaphase (stops the
spindle formation).
CO-stops the krebs cycle(ATP synthesis stops).

16. Meiosis(Reductional division)
 It is the cell division resulting in the formation of four
daughter cells each having half the number of
chromosomes to that of parent cell.
 It occurs in the reproductive cells.
 Farmer and Moore coined the term meiosis(1905).

17. Stages of meiosis
 Meiosis-I
 Prophase I
 Leptotene
 Zygotene
 Pachytene
 Diplotene
 Diakinasis
 Metaphase I
 Anaphase I
 Telophase I
 Meiosis-II
 Prophase II
 Metaphase II
 Anaphase II
 Telophase II

18.  Fluorescent micrographs of
chromosome spreads stained for
DNA and the meiotic cohesin
subunits (A–L) SMC3 and (M–X)
SYN1 in (A–F, M–R) wild type and
(G–L, S–X) rsw4 exposed to 30°C for
2 days. In each panel, the top image
shows a merged image of the DNA
(red) and cohesin signal (green); the
bottom image only shows the
cohesin signal (green) for the same
meiotic spread. (A, G, M, S) Early
zygotene. (B, H, N, T) Pachytene.
(C, I, O, U) Diakinesis. (D, J, P, V)
Metaphase I. (E, K, Q, W) Anaphase
I. (F, L, R, X) Prometaphase
II/Metaphase II. Bar = 10 µm.

19.  Fluorescent micrographs of
meiocytes showing
microtubules (green) and
DNA (blue) for (A–D, I–L)
wild type and (E–H, M–P)
rsw4 exposed to 30°C for 2
days. (A, E) Metaphase I. (B,
C, F, G) anaphase I. (D, H)
Telophase I. (I, M) Metaphase
II. (J, N) Late anaphase II. (K,
O) Telophase II. (L, P) Pre-
cytokenisis. Bar = 10 µm.

20. Prophase I
 It is the longest of all meiotic
phases and very complex.
 It consists of five sub stages.
 Leptotene-
• In this, chromosomes
condense and appear like
inter woven long threads.
• In some animal and plants
chromosomes may be
polarized and form clump on
nuclear membrane. It is
called synizesis or bouquet
formation.

21.  Zygotene
• In this stage synapsis or pairing of
homologous chromosomes takes
place. One of the two
homologous chromosome from
male and other from female
parents.
• A pair of homologous
chromosome(i.e. four
chromatids) form a structure
called synaptonemal complex.
 Pachytene
• During this stage crossing over
takes place. It is an exchange of
equal segments of non-sister
chromatids belonging to two
different but homologous
chromosome.
• The chromosome pair(bivalent)
consist of four chromatids is
called tetrad. Only two of the four
chromatids takes part in crossing
over.

22.  Diplotene
• At the completion of crossing over
the two chromosomes are in
contact at several points along
their length. These point of
contact between homologous
chromosome are known as
chiasmata.
• The homologous chromosome
now start separating from one
another and the chiasma begin to
open. The separation begins at the
centromere and progress towards
the ends. The process is known as
terminalization.
 Diakinesis
• The chromosome continue to
contract and terminalization still
continues.
• The nuclear membrane dissociate
and disappear.
• The spindle fibres begin to appear.

24. Metaphase I
 The chromosomes appear
condensed. The spindle
fibres get attached to the
centromere of two
homologous
chromosomes.
 The chromosomes now
become arranged at the
equater of the cell. Due to
independent assortment
the alignment is random,
which cause diversion.

25. Anaphase I
 The two chromosomes
separate and move towards
the poles due to contraction
of spindle fibres. Here
centromeres do not divide
and the sister chromatids do
not separate. The entire
chromosome with two
chromatid moves to the same
pole. Hence the division is
reductional or disjunctional.
 Each pole of the cell has half
the number of chromosome
as compare to the parent cell.

26. Telophase I
 Nuclear membrane appears
around the group of
chromosomes at each pole of
cell. Thus the daughter nuclei
with half number of
chromosomes are formed.
 After formation of nuclei,
chromosomes pass into a
small
interphase(interkinesis)
before the second meiotic
division. In this phase DNA
replication does not occur.

27. Prophase II
 The chromosome
become short and thick.
 Nuclear membrane
disappear.
 The spindle apparatus is
formed.

28. Metaphase II
 The chromosome get
arranged on the
equatorial plate of the
cell.
 The spindle fibres
attached to the same
centromere.

29. Anaphase II
 The centromere divide
and the chromatids of
each chromosome
separate and move to the
poles.

30. Telophase II
 chromosomes form a
cluster at opposite pole
of cell. Nuclear
membrane reappear to
form two daughter
nuclei.

31. Cytokinesis
 In animal cell, the cleavage
furrow becomes deeper as
spindle breakdown and
finally join to form four
daughter cells.
 In plant cell, the cell plate
is formed to separate the
four daughter cells. It
begins at the Centre of the
cell and proceeds towards
the periphery.

32. Significance of meiosis
 It helps in haploid gamate formation and sexual
reproduction.
 It helps in maintaining the species specific
chromosome number.
 It helps in exchange of genetic material. Thus cause
variation which also leads to evolution.

33. References
 C.B. Power, cell biology, Himalaya publishing house,7th
edition,2017, page no-628-652.
 P. k. Gupta, cell and molecular biology, Rastogi
publications, 3rd edition,2009,page no-287-298.
 A. Bendre, P.C. Pande, concept of botany, Rastogi
publications, 8th edition, 2013,page no-2.167-2.187.
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34. Thank you