Cell division is a very important process in all living organisms. During the division of a cell, DNA replication and cell growth also take place. All these processes, i.e., cell division, DNA replication, and cell growth, hence, have to take place in a coordinated way to ensure correct division and formation of progeny cells containing intact genomes. In eukaryotes, there are two distinct types of cell division: a vegetative division, whereby each daughter cell is genetically identical to the parent cell (mitosis), and a reproductive cell division, whereby the number of chromosomes in the daughter cells is reduced by half to produce haploid gametes (meiosis).

1. MSc, Department of Bioinformatics, KSAWU, Vijayapura 1
Karnataka State Women's University VIJAPUR
SUBJECT : CELL AND MOLECULAR BIOLOGY
SUBJECT CODE : BI. HCT 1.1

2. 1. Cell Division – Introduction
2. Prokaryotes - Cell Division
3. Eukaryotes - Cell Division
A. Mitosis
B. Meiosis
4. Differences Between Mitosis
And Meiosis

3.  All cells are derived from pre-existing cells.
 New cells are produced for growth and to replace damaged
or old cells.
 Cell division differ in prokaryotes (bacteria ) and eukaryotes
( protista, fungi, plants and animals).
 Before a cell becomes too large, it divides, producing 2 or 4
daughter cells.
 Before the cell divides, the DNA is replicated, so each new
cell will have the same genetic information as the parent cell.
1655 – Hooke described ‘cells’ in cork.
INTRODUCTION
MSc, Department of Bioinformatics, KSAWU, Vijayapura 3

4.  Prokaryotes have no nucleus.
 They have a single circular chromosome.
 Prokaryotes simply divide their cells in two by binary
fission , where their genetic material is segregated
equally into two daughter cells.
 There are alternative manners of division, such as
budding, that have been observed.
MSc, Department of Bioinformatics, KSAWU, Vijayapura 4

5. Prokaryotes such as bacteria
divide into 2 identical cells by
the process of binary fission
Single chromosome makes a
copy of itself .
Cell wall forms between the
chromosomes dividing the cell .
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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6. Eukaryotes
 In eukaryotes, there are two distinct types of cell
division:
 A vegetative division, whereby each daughter cell is
genetically identical to the parent cell (mitosis).
 A reproductive cell division, whereby the number of
chromosomes in the daughter cells is reduced by half to
produce haploid gametes (meiosis).
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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7. The sequence of events by which a cell duplicates
its genome, synthesizes the other constituents of
the cell and eventually divides into two daughter
cells is termed as cell cycles.
MSc, Department of Bioinformatics, KSAWU, Vijayapura 7

8. G1 – primary growth phase
S- synthesis; DNA replicated
G2 – secondary growth phase
 collectively theses 3 stages are called interphase
 M – mitosis
 c- cytokinesis
90%
10%
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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9. Interphase – G1 phase
Growth of cell
Duplication of organelles
Synthesis of proteins
Interphase – S phase
DNA synthesis occurs.
DNA replication begins in the
nucleus.
The centriole duplicates in the
cytoplasm.MSc, Department of Bioinformatics,
KSAWU, Vijayapura
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10. 2nd Growth Stage
Occurs after DNA has been duplicated or replicated
All cell organelles & proteins needed for division are
synthesized
Interphase – G 2 phase
MSc, Department of Bioinformatics,
KSAWU, Vijayapura
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11. Includes 2 parts :
1. Mitosis
PROPHASE
PROMATAPHASE
METAPHASE
ANAPHASE
TELOPHASE
2. Cytokinesis
M phase
MSc, Department of Bioinformatics,
KSAWU, Vijayapura
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12. Mitosis is a process of cell division in which chromosome
replicates and get equally distributed into two daughter
cells so that these cells have the same number and type of
chromosome as present in the parent cell.
Mitosis
In 1835, German botanist
Hugo von Mohl
discovered mitosis in cells of
algae Cladophora glomerata.
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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13. Duration : 15 minutes
 Chromosome condenses and coil, they become
visible under light microscope.
 The two sister chromatids of each chromosome
attach at a point called centromere.
 Spindle fibers begin to form from two centrosome,
and they will start moving apart .
PROPHASE
PROMETAPHASE
Duration : 15 minutes
 The nuclear membrane disappears.
 Kinetochore will get attached to the centromere
 The spindle fibers become attached to the
kinetochore
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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14. Duration : 20 minutes
 Spindle fibres attach to kinetochores of
chromosomes.
 Chromosomes are moved to equator and get aligned
along metaphase plate through spindle fibers get
seperated to both poles.
METAPHASE
ANAPHASE
Duration: 3 minutes
Sister chromatids are pulled apart to
opposite poles of the cell by kinetochore
fibers
MSc, Department of Bioinformatics,
KSAWU, Vijayapura
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15. TELOPHASE
Duration : 10 minutes
 Chromosomes cluster at opposite
spindle poles and their identity is
lost as discrete elements.
 Nuclear envelope assembles around
the chromosome clusters.
 Nucleolus, Golgi complex and ER
reform.
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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16.  Cytokinesis is the division of the
cytoplasm
 Results in two separate daughter cells
with identical nuclei
 Occurs at the same time as telophase
CYTOKINESIS
Animal cells Plant cells
Cell membrane is drawn
inward until the
cytoplasm is pinched
into 2 nearly equal parts
Cell plate forms
midway between
the divided nuclei
Cell wall begins to
appear in the cell
plate.MSc, Department of Bioinformatics,
KSAWU, Vijayapura
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17. Summary
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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18. MSc, Department of Bioinformatics, KSAWU, Vijayapura
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19. Meiosis
Formation of Gametes
(Eggs & Sperm)
MSc, Department of Bioinformatics, KSAWU, Vijayapura 19

20. In 1882, British cytologist
Pierre-Joseph van Beneden
he observed that gametes (sperm &
egg) contain half the number of
chromosomes compared to somatic
cells(non reproductive cells).
MEIOSIS
Meiosis - the process of cell division that produces
haploid gametes (half the number of chromosomes:
humans: 23)
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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21. Reduction Division
• Cell undergoes 2 rounds of cell
division:
•Meiosis 1
•Meiosis 2
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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22. Meiosis I
• Preceded by Interphase- chromosomes are replicated
to form sister chromatids
• Sister chromatids are genetically identical and joined
at centromere
• Single centrosome replicates, forming 2 centrosomes
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23. Prophase I
• Individual chromosomes first become visible
– homologous chromosomes become closely
associated in synapsis
– crossing over occurs
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24. Metaphase I
• The homologous chromosomes line up in the equator
of the cell and are still held together
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25. Anaphase I
• Spindle fibers shorten
• The homologous chromosomes are separated (the
sister chromatids are still paired)
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26. Telophase I
• The nuclear membrane reforms around each
daughter nucleus
• Each new cell now contains two sister chromatids
that are NOT identical due to crossing over
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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27. At the end of Meiosis I…
• At the end we have 2 cells
• Each cell contains a haploid number of
chromosomes – 1 copy of each chromosome (for
humans, each haploid cell has 23 chromosomes)
• No DNA replication occurs between Meiosis I
and Meiosis II
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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28. Prophase II
• Nuclear membrane breaks down again
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29. Metaphase II
• The chromosomes line up in the middle of
the cell.
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30. Anaphase II
• The spindle fibers shorten and the sister
chromatids move to opposite poles.
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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31. Telophase II
• Nuclear envelope re-forms around the four
sets of daughter chromosomes.
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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32. At the end of Meiosis II…
• At the end of Meiosis II, there are 4
haploid cells.
• No two of these haploid cells are alike due
to crossing over.
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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33. Comparison of Divisions
Mitosis Meiosis
Number of
divisions
1
2
Number of
daughter cells
2 4
Genetically
identical?
Yes No
Chromosome # Same as parent Half of parent
Where Somatic cells Germ cells
When Throughout life At sexual maturity
Role Growth and repair Sexual reproduction
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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34. Reference
MSc, Department of Bioinformatics, KSAWU, Vijayapura
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1. ^ Cells : building blocks of life. Maton, Anthea. (3rd ed.). Upper Saddle
River, N.J.: Prentice-Hall. 1997. pp. 70–74. ISBN 978-0134234762.
OCLC 37049921.
2. ^ Cell division : theory, variants, and degradation. Golitsin, Yuri N.,
Krylov, Mikhail C. New York: Nova Science Publishers. 2010. p. 137.
ISBN 9781611225938. OCLC 669515286.
3. ^ Molecular cell biology 5th edition LODISH . BREK . BREAK .
MATSUDAIRA. KAISER. KRIEGER. SCOTT. ZIPURSKY. DARNELL.

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36. MSc, Department of Bioinformatics, KSAWU, Vijayapura 36