Cell division

1. Mitotic cell division
RINI JOSEPH

2. Definition
 Mitosis is a process of nuclear division in
eukaryotic cells that occurs when a parent
cell divides to produce two identical daughter
cells .
 During cell division , mitosis refers
specifically to the separation of the
duplicated genetic material carried in the
nucleus .

4. Phases of mitosis
Mitosis consists of four basic phases :
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

5. EARLY PROPHASE :
In early prophase , the cell starts to break
down some structures and built others up
setting the stage for division of the
chromosomes .
» The chromosomes start to condense.
» Mitotic spindle begin to from –
microtubules , strong fibers that are part of the
cells “skeletal ”.
» The nucleolus a part of the nucleus where
ribosomes are ,made disappears .

6. Prophase:
 The chromosomes condense and become
visible - chromatids .
 The centrioles form and move toward
opposite ends of the cell(“the poles”)
 The nuclear membrane dissolves
 The mitotic spindle forms .
 Spindle fibers from each centriole attach to
each sister chromatid at the kinetochore.

7.  Creating kinetochores
 Microtubules attach at kinetochores
 Connect centromeres to centrioles
 Chromosomes begins moving.

8. Metaphase:
 Chromosomes align along middle of cell
 Metaphase plate
 Meta=middle
 Spindle fibers coordinate movement
 Helps to ensures chromosomes separate properly
 So each new nucleus receives only one copy of
each chromosome

10. Anaphase
 Sister chromatids separate at kinetochores
 Move to opposite poles
 Pulled at centromeres
 Pulled by motor proteins “waking” along
microtubules
 Increased production of ATP by mitochondria
 Poles move farther apart
 Polar microtubules lengthen

12. Separation of chromatids
 In anaphase, proteins holding together sister
chromatids are inactivated.
 Separate to become individual chromosomes.
Chromosome movement
 Kinetochores use motor proteins that “walk”
chromosome along attached microtubules.
 Microtubules shortens by dismanting at
kinetochore(chromosome ) end.

13. Telophase
 Chromosomes arrive at opposite poles
 Daughter nuclei form
 Nucleoli form
 Chromosome disperse
 No longer visible under light microscope
 Spindle fibers disperse
 Cytokinesis begins
 Cell division

15. Cytokinesis
 Cytokinesis is often mistakenly thought to be
the final part of telophase.
 Cytokinesis is a separate process that beings at
the same time as telophase.
 Cytokinesis is technically not even a phase of
mitosis , but rather a separate process
 Necessary for completing cell division .
 In animal cells, a cleavage furrow (pinch)
containing a contractile ring develops where
the metaphase plate used to be pinching off
the separated nuclei.

16.  In both animal and plants cells, cell division
is also driven by vesicles derived from the
golgi apparatus, which move along
microtubules to the middle of the cell
 In plant cell this structure coalesces into a
cell plate at the centre of phargmoplast and
develops into a cell wall, separating the two
nuclei.