2. 1. Why do cells divide?
2. How do cells divide?
3. Stages of Mitosis
a) Interphase
b) Prophase
c) Metaphase
d) Anaphase
e) Telophase
f) Cytokinesis
Index
3. Biology is the only subject in which
multiplication is the same thing as division…
4. You started as a cell smaller than
a period at the end of a sentence…
• Where it all began…
5. • And now look at you…
How did you
get from there
to here?
6. Going from egg to baby….
the original fertilized egg has to divide…
and divide…
and divide…
and divide…
• Getting from there to here…
7. For reproduction
For growth
from fertilized egg to multi-celled
organism
For repair & renewal
replace cells that die from normal wear
& tear or from injury
• Why do cells divide?
9. Mitosis is the division of somatic cells (body cells)
It is the process in which the nucleus divides to form two new nuclei.
The chromosomal number remains unchanged.
•How do cells divide?
Somatic Cell
Daughter Cells
10. •Pop quiz
1. Mitosis in body cells results in _____________.
4 daughter
cells
2 daughter
cells
1dupilcate
cell
11. • The process of mitosis is fast and highly complex. The sequence of
events is divided into stages corresponding to the completion of one
set of activities and the start of the next. These stages in order of
occurrence are-
• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis
•Stages of Mitosis
12. •Pop quiz
1. The order of the stages in Mitosis is
Interphase-Anaphase-Telophase-
Prophase-Metaphase
Interphase-Prophase-Metaphase-
Anaphase-Telophase
Interphase-Metaphase-Anaphase-
Prophase-Telophase
13. • The cell is in Interphase for most of its life cycle.
• In Interphase, the cell “prepares” for division by
• obtaining nutrients and growing,
• copying its DNA, and
• replicating its centrioles.
• The nuclear membrane is still visible.
• Chromatin has not yet condensed into chromosomes in
this stage.
• The nucleolus is still present.
•Interphase
chromatin threads
nucleolus
centrioles
14. •Pop quiz
1. Body cells are in ________________ stage for most of its life cycle.
Anaphase
Interphase
Prophase
15. •Pop quiz
1. Body cells are in ________________ stage for most of its life cycle.
Anaphase
Interphase
Prophase
16. • In Prophase:-
• DNA becomes visible as chromosomes
• Nuclear membrane dissolves
• Centrioles migrate to opposite poles
• Spindle fibers form
•Prophase
chromatids
centrioles
spindle fibers
nucleus
17. •Pop quiz
1. Spindle fibers form in __________ stage.
Anaphase
Prophase
Metaphase
18. In Metaphase:-
• Spindle fibers attach to centromeres
• Chromosomes line up at midline of the cell
• This organization helps to ensure that in the next
phase, when the chromosomes are separated, each
new nucleus will receive only one copy of each
chromosome.
•Metaphase
equatorial plane
centromeres
19. •Pop quiz
1. In Metaphase chromosomes line up along the _________
Equatorial
Plane
Poles
Don’t line up
20. • In anaphase, the spindle fibres shorten, which splits
the chromosome strand into two separate, sister
chromatids. The sister chromatids are pulled to
opposite ends of the cell.
• This is the only stage in the life of a cell where the
chromosome number is greater than a 2n (or diploid)
count
•Anaphase
sister chromatids
21. •Pop quiz
1. Only stage where chromosomal number is greater
than 2n is ___________
Metaphase
Anaphase
Telophase
22. • The chromosomes finally reach opposite poles (the
ends) of the cell.
• The nuclear envelope and nucleolus reform around
each new set of chromosomes. The chromosomes
disperse and are no longer visible.
• Spindle fibers disperse and are no longer visible.
•Telophase
nuclear envelope
cytoplasm
begins to divide
23. • Cytokinesis marks the end of mitosis in the cell cycle.
It is where the cell officially splits into two separate
cells, called daughter cells. Each daughter cell now
has the same number of chromosomes as the original
cell before mitosis. The cell splits when a furrow forms
that pinches the cell in two.
•Cytokinesis
contractile ring
centrosome
nuclear envelope
decondensed
chromosome
24. •Pop quiz
1.The chromosome reach the poles of the cell in
___________ stage.
Prophase
Anaphase
Telophase
25. • Prophase:
• Chromosomes condense
• Nuclear envelope disappears
• centrosomes move to opposite sides of the cell
• Spindle forms and attaches to centromeres on the chromosomes
• Metaphase
• Chromosomes lined up on equator of spindle
• centrosomes at opposite ends of cell
• Anaphase
• Centromeres divide: each 2-chromatid chromosome becomes two 1-chromatid
chromosomes
• Chromosomes pulled to opposite poles by the spindle
• Telophase
• Chromosomes de-condense
• Nuclear envelope reappears
• Cytokinesis: the cytoplasm is divided into 2 cells
Exit
• Summary of Mitosis
