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DR. HIMANI SINGH
M.Sc., Ph.D
BIOTECHNOLOGY

? A cell enters mitosis, its duplicated chromosomes condense
into rod- shaped bodies (prophase)
? As mitosis progresses, the chromosomes migrate to the
equatorial plane of the cell (metaphase)
? In mitosis, the centromere that holds the sister chromatids of
a duplicates chromosomes together splits, and the sister
chromatids separate (or disjoin) from each other (anaphase)
? As mitosis comes to en end, the chromosomes decondense
and a nuclear membrane reforms around them (telophase)
? Each daughter cell produced by mitosis and cytokinesis has
the same set of chromosomes; thus daughter cells are
genetically identical.

? During mitosis, the chromosomes
shorten and thicken
? They ��condense�� out of the
chromatin network and individual
chromosomes ��decondens�� the
chromatin network is re-formed.
? When mitosis begins each
chromosome has already been
duplicated, and the duplicated
called sister chromatids, they
intimately associated with each
other and are joined at the
chromosome��s centromere.
? Microtubules: Distribution of
duplicated chromosomes to the
daughter cells is organized and
executed by microtubules, are
components of the cytoskeleton.
These fibers composed of
proteins (tubulins), attached to the
chromosomes and move them
about within the dividing mother
cell.

? The microtubules assemble into a
complex array called the spindle.
Formation of the spindle depends on
microtubules organizing centers
(MTOCS), are formed in the
cytoplasm usually near to the
nucleus.
? The MTOCS are differentiated into
small organelles called centrosomes.
Each centrosomes contains two
barrel shaped centrioles.
? Pericentriolar material: A
centrosome consists of two barrel-
shaped centrioles embedded in a
matrix of proteins known as the
pericentriolar material (PCM). The
PCM serves as a platform
for protein complexes that regulate
organelle
Spindle
fibers

? S is the period in which
the chromosomes are
duplicated, an events
that require DNA
synthesis, to which the
label ��S�� refers.
? The M phase in the cell
cycle is the time, when
the mother cell actually
divides. Has usually
two components:
(1) Mitosis
(2) Cytokinesis
The label ��M�� refers to
the term mitosis, is
derived from Greek
word for thread.
? The G1 and G2 phase
are ��gaps�� between the
S and M phases.
This cycle is 24 hours long, a series of phases
that collectively form the CELL CYCLE

? Interphase: during this period individual chromosomes cannot
be seen, which may be quite lengthy. Is the phase of the cell
cycle in which a typical cell spends most of its life. During
interphase, the cell gets itself ready for mitosis or meiosis.
? Prophase: Prophase is the first stage of cell division in both
mitosis and meiosis. Beginning after interphase, DNA has
already been replicated when the cell enters prophase. The main
occurrences in prophase are the condensation of the chromatin
and the disappearance of the nucleolus.
? Metaphase: Chromosomes aligned at metaphase plate halfway
between the poles. Spindle microtubules attached to the
kinetochores.
? Anaphase: Sister chromatids of duplicated chromosomes are
separated from each other during this phase, this separation is
accomplished by shortening the microtubules attached to the
kinetochores.
? Telophase: The process that separates the duplicated genetic
material carried in the nucleus of a parent cell into two identical

6
Cleavag
e furrow
splits cell
in two
5
Nuclear
envelope
re-forms
4
Separation
of sister
kinetochor
es begins
anaphase
3
Chromosomes move to metaphase
plate
2
Nuclear
envelop
e
breaks
down
1
Centrosom
es
duplicates
chromosom
es begin to
condense
and
become
visible

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Mitosis, cell division

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