Types of phases are described in this ppt......... Thanks to My Bio Tr - Mrs. Alarmelu Natchiar.........

2. • Cell division:- DNA replication & Cell
growth
• They takes place in a coordinated way
to ensure correct division & formation
of progeny cells which contains intact
genomes.
• Cell cycle- the events by which a cell
duplicates its genome ,synthesises the
constituents of the cell divides into
daughter cells.

3. • Cell growth is a continuous process but
DNA synthesis takes only once in this
stage.
• DNA Daughter nuclei
(complex series of event – cell division).
• DNA processes are under genetic
control.

4. • Eukaryotic cell – divide once in approx. every
24 hrs.
• This varies from organism – organism & cell –
cell type.
• E.g. Yeast – the cell cycle of yeast progress in
90 minutes.

5.  There are 2 basic phases:-
1) M Phase(mitosis phase) – the actual cell
division/mitosis occurs.
2) Interphase - phase between 2 successive M
phases.
 Duration of Interphase is 24 hrs in a cell
cycle.
 Karyokinesis – (nuclear division) separation of
daughter chromosomes.
 Cytokinesis – division of cytoplasm.

6. Cytokinesis Karyokinesis

7. The Interphase is divided into 3 phases:-
a) G1 Phase (Gap 1)
Interval Between mitosis & initiation of DNA
replication.
It is also known as growth phase & the cell is
metabolically active.
b) S Phase (Synthesis)
DNA synthesis & replication takes place
c) G2 Phase (Gap 2)
Proteins are synthesized in preparation for mitosis
while cell growth continues.

8. A diagrammatic view of cell cycle indicating
formation of two cells from one cell.

9. • Some cells do not divide further exit G1 Phase
to enter an interactive stage – Quiescent stage
(G0).
M phase(mitosis) involve reorganization of
virtually all components of the cell.
Mitosis is divided into four stages
a) Prophase
b) Metaphase
c) Anaphase
d) Telophase

10. Equational Division
The number of chromosomes in the parent
and progeny cells is the same.
46
23 23

11. • It is marked by the initiation of condensation of
chromosomal material.
• Chromosomal material mitotic
chromosomes.
• Spindle fiber – a set of thread like structures made by
an organelle called centriole.
• The centriole moves towards the opposite poles of the
cell.
• Two (sister) chromatids attach together at the
centromere.

14. Prophase – diagrammatic view

15. • Disintegration(breakup) of the nuclear envelope
marks the start of metaphase.
• In this phase the chromosomes are made of
sister chromatids held together by the
centromere.
• Kinetochores (site of attachment of spindle
fibers)– small disc shaped structures at the
surface of the centromere.

16. • Chromosomes moves to the centre of the
cell(spindle equator).
• One chromatid of each chromosome connected n
kinetochore to spindle fibers from one pole
• Sister chromatids connected in the opposite
poles by the kinetochores.
• Metaphase Plate – plane of alignment of the
chromosomes at the metaphase.

17. Metaphase – diagrammatic view