CELL DIVISION( BINARY FISSION,MITOSIS, MEIOSIS)

1. CELL DIVISION
TO: SUBASH CHANDER BY:ANIL KUMAR(2011A14BIV)

2. CELL
The cell (from Latin cella, meaning
"small room") is the basic structural,
functional, and biological unit of all
known living organisms

3. DISCOVERY
The cell was discovered by Robert Hooke in
1665.
His book Micrograhia
Thin slices of bottle cork.

4. Robert hook’s microscope Micrograph of cell

5. CELL THEORY

6. Cell theory has 3 basic points:
• All living things are made of cells.
• The cell is the smallest living thing that can
perform all the functions of life.
• All cells must come from pre-existing cells.

7. Cell division
Binary fission
Mitosis
Meiosis

8. BINARY FISSION
The cell divides into
two nearly equal sized
daughter cells.
The genetic material is
also equally split

9. MITOSIS
Mitosis is the process by
which chromosomes in a cell
nucleus are separated into two
identical sets of chromosomes, each
in its own nucleus

10. DISCOVERY
German zoologist Otto Bütschli
1843-1905
Term coined by Walther Flemming in 1882.

11. PHASES
o Interphase
o Prophase
o Metaphase
o Anaphase
o Telophase
o Cytokinesis

12. INTERPHASE
It is the longest phase.
G1
S
G2

13. G1 - first gapS - DNA synthesis
(replication)
G2 - second gap
M - mitosis

14. G1 (FIRST GAP)
The cell grows and functions normally.
A high amount of protein synthesis occurs .
The volume of cytoplasm increases.
Mitochondria and chloroplasts divide.

15. SYNTHESIS (S)
The cell duplicates its DNA .
This is also known as the
Swanson phase.

16. G2 (Gap 2)
The cell resumes its growth in
preparation for division.

17. G0 (Gap zero)
Some cells that do not divide often
or ever, enter a stage called G0 .
G0 phase semi-permanentally e.g.,
some liver, kidney, stomach
cells.

18. PROPHASE
• The chromatin becomes visible.
• The chromatin condenses into
double rod-shaped structures
called chromosomes.
• The centrosomes move to
opposite poles of the cell, forming
a bridge of spindle fibers.
• The nucleolus disperses.
ONION CELL

19. METAPHASE
Chromosomes
carrying genetic information
align in the equator of the cell.
Alignment is due to the
pulling powers generated by
the opposing kinetochore
microtubules.
ONION CELL

20. micrograph

21. ANAPHASE
Chromosomes are split and the sister
chromatids move to opposite poles of
the cell.
ONION CELL

22. TELOPHASE
Two daughter nuclei form
in each daughter cell.
forming nuclear
envelopes around each
nucleus.
Onion cell

23. CYTOKINENSIS
It is the process in which
the cytoplasm of a single cell
is divided to form two daughter
cells.
Plant cells construct a cell
plate in the middle of the cell.
Onion cell

24. Onion (Allium) cells in different phases of the cell cycle
enlarged 800 diameters.
a. non-dividing cells
b. nuclei preparing for division .
c. dividing cells showing mitotic figures.
e. pair of daughter-cells shortly after division.

25. MEIOSIS
It is a specialized type of cell division which
reduces the chromosome number by half.
This process occurs in all sexually
reproducing eukaryotes (both single-celled
and multicellular) including animals, plants,
and fungi.

26. HISTORY
Meiosis was discovered and described
for the first time in sea urchin eggs in
1876 by the German biologist Oscar
Hertwig.
The term meiosis was introduced to
biology by J.B. Farmer and J.E.S.
Moore in 1905.

27. PHASES
Meiosis I
 Prophase I
• Leptotene
• Zygotene
• Pachytene
• Diplotene
• Diakinesis
 Metaphase I
 Anaphase I
 Telophase I
Meiosis II

28. PROPHASE I
Leptotene :
Individual chromosomes—each
consisting of two sister
chromatids—condense from the
diffuse interphase conformation
into visible strands within the
nucleus.

29. ZYGOTENE
At this stage, the synapsis
(pairing/coming together) of
homologous chromosomes takes
place.
Synaptonemal complex

30. PCHYTENE
It is the stage when chromosomal
crossover (crossing over) occurs.
Nonsister chromatids of homologous
chromosomes may exchange
segments over regions of homology.
At the sites where exchange
happens, chiasmata form

31. DEPLOTENE
The synaptonemal complex degrades
and homologous chromosomes separate
.
The chiasmata remain on the
chromosomes until they are severed in
anaphase I om one another a little.

32. DIAKINENSIS
This is the first point in meiosis where the
four parts of the tetrads are actually
visible.
The nucleoli disappear, the nuclear
membrane disintegrates into vesicles, and
the meiotic spindle begins to form.

34. METAPHASE I
Homologous pairs move
together along the
metaphase plate.
As kinetochore
microtubules from both
centrioles attach to their
respective kinetochores.
Lily ovulary cell

35. ANAPHASE I
Kinetochore microtubules shorten.
Pulling homologous
chromosomes to opposite poles.
This allows the sister chromatids
to remain together while
homologs are segregated.
Lilium anther

36. TELOPHASE I
The chromosomes arrive at the
poles.
Each daughter cell now has half
the number of chromosomes
but each chromosome
consists of a pair of
chromatids.
Lily pollen

37. MEIOSIS II
 Prophase II
 Metaphase II
 Anaphase II
 Telophase II

38. PROPHASE II
The disappearance of the
nucleoli
and the nuclear
envelope again.
Centrioles move to the
polar regions .
Lilium anther

39. METAPHASE II
Single chromosomes align on the
metaphase plate .
Lily pollen

40. ANAPHASE II
The centromeres separate.
The two chromatids of
each chromosome move to
opposite poles on the
spindle.
The separated chromatids
are now called
chromosomes in their own
right. Lily pollen

41. TELOPHASE II
A nuclear envelope forms
around each set of
chromosomes.
LILY POLLEN

42. FOUR HAPLOID CELL
FORM
A nuclear envelope forms around
each set of chromosomes.

43. THANKS