This document provides an overview of cell division through mitosis. It begins by defining chromosomes and describing how DNA is packaged within cells. It then explains the stages of the cell cycle, including interphase and its subphases. The document delves into the stages of mitosis - prophase, metaphase, anaphase and telophase. It describes how identical daughter cells are produced and discusses the roles of centrioles, centrosomes and spindle fibers. The document concludes by comparing mitosis in animal and plant cells, focusing on differences in cytokinesis.

1. BIOLOGY FORM 4
CHAPTER 5 PART 1
CELL DIVISION - MITOSIS

3. CHROMOSOMES:
• carry the genetic code
• contain all characters of cells
Chromosomes
Composed of chromatin – a
complex of DNA and proteins

4. DNA is packed
The coiling and condensing of DNA

5. The total extended
length of DNA in a
human cell is
nearly 2m, but this
must be fit into a
nucleus with a
diameter of only 5
to 10μm.

6. Number of Chromosomes
Ant: 2 Fruit Flies: 8 Carrots: 20
Shrimp: 254
Turkey: 82
Dog: 48
Adders tongue
(Fern): 1260
Largest number of
chromosomes

7. The human genome (the total number of
chromosomes) in humans is:
23 homologous chromosomal pairs
Set 23:
Sex chromosomes
Set 23:
Sex chromosomes

8. HHoommoollooggoouuss cchhrroommoossoommeess
 Paired
chromosomes
- From maternal &
paternal sources
- control same
inherited characters
- homologous = same
information

9. Why are chromosomes drawn in a
different colour?
Chromosomes are of either
MATERNAL or PATERNAL origin.
from Mum from Dad

10. KKeeeeppiinngg CCeellllss IIddeennttiiccaall
TThhee iinnssttrruuccttiioonnss ffoorr
mmaakkiinngg cceellll ppaarrttss
aarree eennccooddeedd iinn tthhee
DDNNAA,, ssoo eeaacchh nneeww
cceellll mmuusstt ggeett aa
ccoommpplleettee sseett ooff tthhee
DDNNAA mmoolleeccuulleess

11. DDNNAA RReepplliiccaattiioonn
DDNNAA mmuusstt bbee
ccooppiieedd oorr
rreepplliiccaatteedd
bbeeffoorree cceellll
ddiivviissiioonn
EEaacchh nneeww cceellll
wwiillll tthheenn hhaavvee aann
iiddeennttiiccaall ccooppyy ooff
tthhee DDNNAA
OOrriiggiinnaall DDNNAA
ssttrraanndd
TTwwoo nneeww,,
iiddeennttiiccaall DDNNAA
ssttrraannddss

12. IIddeennttiiccaall DDaauugghhtteerr CCeellllss
PPaarreenntt CCeellll
TTwwoo
iiddeennttiiccaall
ddaauugghhtteerr
cceellllss

13. CELL CYCLE
- preparation for cell division

14. Three Main stages in the Cell Cycle
3. Interphase
(growth
- 90% of the time)
2. Cytokinesis
(Cytoplasm
division)
1. Mitosis
(nuclear division)

15. Interphase has three subphases:
3. G2
(Gap 2)
2. S phase
(DNA synthesis)
1. G1
(Gap 1)

16. What happens in each subphase?
synthesis and
replication of
organelles
synthesis of
proteins and RNA
DDNNAA ssyynntthheessiiss
cells that
do not
divide again
enter G0

17. Three organelles replicate:
Mitochondria
Chloroplasts
Centrioles

18. The length of the Cell Cycle depends
on:
The type of cell:
 usually the more
specialised the cell
the less likely it is
to divide
External factors e.g.:
temperature
food
oxygen supplies
RBC are
replaced at
a rate of 2-3
million/sec Nerve cells
usually never
divide

19. © 2003 John Wiley and Sons Publishers

20. 21
SSkkeettcchh tthhee CCeellll CCyyccllee
DDaauugghhtteerr
CCeellllss
DDNNAA CCooppiieedd
CCeellllss
MMaattuurree
CCeellllss pprreeppaarree ffoorr
DDiivviissiioonn
CCeellll DDiivviiddeess iinnttoo
IIddeennttiiccaall cceellllss

21. Question:
Suggest explanations for the following
observation.
Interphase is not a static stage of
the cell cycle. (2)
Proteins and RNA are synthesised,
DNA is replicated and organelles are
synthesised or replicated.

22. Question :
This question is concerned with cell division.
Give a brief description of the Cell Cycle. (2)
Nuclear division is followed by cytokinesis which
results in two cells.
Each cell enters interphase where proteins and RNA
are synthesized during the G1 phase.
DNA replicates during the S phase and organelles are
synthesized or replicated during the G2 phase.

23. Question:
The graph below illustrates how the quantity of
DNA, within a mammalian somatic cell, varies
during different phases of the cell’s cycle.
Additionally the graph shows the two growth
phases, G1 and G2, which are separated by an
intermediate phase S.
a) In terms of the
graph above, explain
what is happening
within the cell during
phase S. (2)

24. DNA replicates. Each chromosome consists of two
sister chromatids.
b)State ONE process other than cell growth which
occurs during phase G2. (1)
Organelles are synthesised or they replicate.

25. Cells divide for three reasons:
1.For growth e.g.
formation of a
bud in Hydra
2. To produce
gametes or spores
3.To replace
damaged cells
Mucor Salmon gametes mixing

26. TWO types of cells in the body
Non-reproductive
or somatic cells
Non-reproductive
or somatic cells
Gametes &
Spores
Gametes &
Spores
diploid number
of chromosomes (2n)
phagocyte
neurones
haploid number (n)
spermatozoa
pollen grains
(microspores)

27. Life cycle of animals
Human
Human
Haploid(n) – 23 chromosomes
Haploid(n) – 23 chromosomes
Diploid Diploid ((22nn)) – – 4 466 c chhrroommoossoommeess

28. types of nuclear division

29. - the process by which a cell nucleus
divides to produce two daughter
nuclei containing identical sets of
chromosomes to the parent cell
Mitosis in
root tip

30. - the process by which a cell nucleus
divides to produce four daughter nuclei
each containing half the number of
chromosomes of the original nucleus
- also called reduction division
Meiosis forms the ovum and
spermatozoa in animals.

31. MITOSIS

32. SSiiggnniiffiiccaannccee ooff mmiittoossiiss
3. Regeneration and cell
replacement
1. Growth
2. Replace dead & damaged cells

33. Binary fission
in Amoeba
Budding in Yeast
4. Asexual reproduction
 Single-celled eukaryotes reproduce
asexually
 Simple multicellular eukaryotes
reproduce asexually
Hydra by budding

34. Mitosis occurs in
Animals
Animals
In Non-reproductive
or somatic cells
In Non-reproductive
or somatic cells
All cells in the body
except reproductive cells
phagocyte
Plants
•In meristem cells
•Tip of root /shoot

35. Centromeres, centrioles and
centrosomes
Centromere
is a point of constriction
on the chromosome

36. Centrioles
organelles in the cytoplasm
only found in animals cells
absent in higher plants
occur in pairs
lie at right angles to each other
able to self replicate
Mitotic
centre
(centrosome)
Mitotic
centre
(centrosome)
Centriole

37. Centrosomes
 are organelles located near the nucleus
 are not membrane-bound and serve as a
mitotic centre in animals – absent in plants
 divide and migrate to opposite poles of the
cell during mitosis

38. Centrosomes
 centrosomes and NOT centrioles are
responsible to assemble the spindle fibres
Spindle fibres
 formed during mitosis and meiosis
 it arranges the chromosomes into their
correct positions in preparation for cell
division.
Spindle
fibres

39. The spindle serves as a:
1. ‘railroad track’ along which the
chromosomes will move
2. framework keeping the two poles
apart

40. NNOO
The spindle fibres
originate from other
mitotic centres

41. Interphase: A stage prior to mitosis
Animal Cell
Plant Cell

42. Interphase – prior to mitosis
each chromosome now exists as a pair of
chromatids joined together by a centromere

43. Interphase – prior to mitosis
at this stage each cell is 4n (four copies of
each DNA molecule, two in each
chromosome of a homologous pair)
A homologous pair Four copies of each
DNA molecule

44. Interphase – prior to mitosis
Chromosomes:
 are long & thin
 dispersed in nucleus
 cannot be seen individually
Centrioles have replicated
Diffused
chromosomes

45. MITOSIS

46. G1
S
telophase
anaphase
metaphase
prophase
Mitosis G2
interphase
Stages of
mitosis in the
cell cycle

47. FFoouurr MMiittoottiicc SSttaaggeess
PPrroopphhaassee
MMeettaapphhaassee
AAnnaapphhaassee
TTeelloopphhaassee

48. Parent cell
Chromosomes are
copied and double
in number
Chromosomes
now split
2 daughter cells
identical to original

49. 52
MMiittoottiicc SSttaaggeess

50. PROPHASE
usually the longest phase of division
the chromosomes shorten and thicken by
coiling: condensation
individual chromosomes can be seen

51. LLaattee PPrroopphhaassee
NNuucclleeuuss && NNuucclleeoolluuss hhaavvee ddiissiinntteeggrraatteedd
CChhrroommoossoommeess

52. PROPHASE
in animal cells:
 the centrioles move to opposite poles of the cell
 asters form Asters: short microtubules
radiating from the centrioles
Function of asters:
help to manipulate chromosomes
during nuclear division to ensure
that each daughter cell has the
appropriate complement of
chromosomes

53. PROPHASE
 the nucleolus disappear
the nuclear membrane
breaks up
spindle fibre is formed

54. PROPHASE
Animal Cell Plant Cell
Spindle fibers

55. What is 2n for this cell? 2n = 8

56. RReevviieeww ooff PPrroopphhaassee
WWhhaatt tthhee cceellll llooookkss lliikkee
WWhhaatt’’ss hhaappppeenniinngg

57. imaginary plane
through the
center of the cell
where the
chromosomes
align

58. METAPHASE
Chromosomes line up around the equator of the
spindle, attached by their centromeres to the spindle
fibres.
AAnniimmaall CCeellll
PPllaanntt CCeellll

59. 70
MMeettaapphhaassee
CChhrroommoossoommeess
lliinneedd aatt tthhee
EEqquuaattoorr
AAsstteerrss aatt tthhee
ppoolleess
SSppiinnddllee
FFiibbeerrss

60. 71
MMeettaapphhaassee
AAsstteerr
CChhrroommoossoommeess aatt EEqquuaattoorr

61. ANAPHASE
 this stage is very rapid
 the centromeres split into two

62. ANAPHASE
 the spindle fibres pull the
daughter centromeres to
opposite poles
 the separated chromatids are pulled behind
the centromeres

63. Why are the chromosomes ‘V’ shaped?
As the chromosome is pulled towards the pole
at the centromere.

64. Chromatid attachment and separation

65. ANAPHASE
Animal Cell Plant Cell

66. AAnnaapphhaassee
SSiisstteerr
CChhrroommaattiiddss
bbeeiinngg
sseeppaarraatteedd

67. AAnnaapphhaassee RReevviieeww
WWhhaatt tthhee cceellll
llooookkss lliikkee
WWhhaatt’’ss
ooccccuurrrriinngg

68. TELOPHASE
 the chromosomes:
 reach the poles of the cell
 uncoil and lengthen
 spindle fibres disintegrate
 nuclear envelope re-forms
 nucleoli reappear
 mitosis is complete at the
end of telophase

69. TELOPHASE can be viewed as a reversal
of prophase, bringing the cell back to the
state of interphase
Animal Cell Plant Cell

70. CCoommppaarriissoonn ooff AAnnaapphhaassee && TTeelloopphhaassee
82

71. IIddeennttiiccaall DDaauugghhtteerr CCeellllss
CChhrroommoossoommee nnuummbbeerr tthhee ssaammee,, bbuutt cceellllss
ssmmaalllleerr tthhaann ppaarreenntt cceellll
WWhhaatt iiss
tthhee 22nn oorr
ddiippllooiidd
nnuummbbeerr??
22

72. RReevviieeww
ooff
MMiittoossiiss
PPrroopphhaassee MMeettaapphhaassee AAnnaapphhaassee TTeelloopphhaassee CCyyttookkiinneessiiss

73. Fig. 12.5 left
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

74. Fig. 12.5 right
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

75. AAmmoouunntt ooff DDNNAA dduurriinngg cceellll ccyyccllee

76. Cell division is still not complete at the
end of mitosis: as the division of the
cytoplasm has not yet begun
cytokinesis:
the division of the cytoplasm
cytokinesis normally:
 follows telophase
 leads into the G1 phase
of interphase

77. Cytokinesis occurs differently in
animal and plant cells

78. Cytokinesis in animal cells
Microfilaments draw
in the cell surface
membrane to form a
cleavage furrow

79. Cytokinesis in animal cells

80. Cytokinesis in plant cells
Cell Plate Forming in Plant
Cells

81. Cytokinesis: Plant Cells
Cell Plate Formation
Vesicles from the
Golgi apparatus
appear at the
equatorial plate.
Contents of
vesicles form the
cell plate – the
beginning of the
new cell wall.
These fuse to form
new plasma
membrane.

82. Cytokinesis in plant cells

83. Mitosis: plant vs animal cells
Plant cell Animal Cell
Centrioles,
Centrosomes
& Aster
Absent Present
Cytokinesis Cell plate
formation
Cleavage
furrow

84. Mitosis – Bone Cell Slides
1 2
Parent cell Chromosomes
copied
3 4 5
Cells
split
Copies separating 2 daughter cells

86. Interphase & Mitosis in Plant cells
Interphase Early Prophase Late Prophase
Metaphase
Early Anaphase
Telophase
Late Anaphase
Daughter cells

87. MMiittoossiiss AAnniimmaattiioonn
NNaammee eeaacchh ssttaaggee aass yyoouu sseeee iitt ooccccuurr??

88. IInntteerrpphhaassee
PPrroopphhaassee
MMeettaapphhaassee
TTeelloopphhaassee
AAnnaapphhaassee
NNaammee tthhee MMiittoottiicc
SSttaaggeess::
NNaammee tthhiiss??
NNaammee tthhiiss??

89. Question:
A researcher is provided with onion bulbs which are
sprouting following dormancy. She intends to use these
bulbs to study mitosis in onion cells.
Which parts of the bulb are suitable for this purpose?
2-3 mm from the root tips

90. Q: Account for the changes in the quantity of DNA in
the cell during mitosis. (2)
At the end of mitosis, quantity of DNA returns to the
original value as sister chromatids separate.
M
G1
S
G2

91. Question:
The drawing shows a stage of mitosis
in an animal cell.
a)Name this stage of mitosis.
Anaphase
b) Describe and explain what happens
during this stage which ensures that two
genetically identical cells are produced.
The centromere splits and the sister
chromatids carrying the same genetic
information move to opposite poles.

92. The table shows the average duration of each stage of
the cell cycle in the cells of a mammalian embryo.
Give one piece of evidence from the table which
indicates that these cells are multiplying rapidly.
Stage Mean duration /
minutes
Interphase 12
Prophase 50
Metaphase 15
Anaphase 10
Telophase 42
Interphase is short.

93. Question :
A student examined the cells in the garlic root
tip under the microscope, and obtained the
following data.
What do you conclude?
Stage Number of cells
Prophase 74
Metaphase 18
Anaphase 8
Telophase 10
Prophase is the
LONGEST phase
and anaphase
the SHORTEST.

94. Question:
A scientist intends to observe mitosis in cells of the
common onion (Allium cepa).
1. Which part of the onion plant should the
scientist use for observing cells undergoing
mitosis? (1)
Root tip.
2. Why is this part of the plant particularly
suitable for this purpose? (2)
The root tip is a growing point in plants. It
contains a meristematic region where cells are
continuously dividing.

95. 3.Describe how the scientist would process
the specimen (the plant structure referred to
in Question 1) in order to be able to observe
mitosis through a light microscope. Your
answer should refer the steps required to
prepare the specimen, to the staining
procedure and to the temporary mounting of
the specimen on a microscope slide. (9)

97. The tips have been
stained red with
Feulgen stain.
AAcceettiicc oorrcceeiinn ssttaaiinn
ccaann bbee uusseedd ttoooo..

98. MMiittoossiiss iinn OOnniioonn RRoooott TTiippss
DDoo yyoouu sseeee aannyy ssttaaggeess ooff mmiittoossiiss??

99. 113
IIddeennttiiffyy tthhee SSttaaggeess
EEaarrllyy,, MMiiddddllee,, & LLaattee PPrroopphhaassee
LLaattee PPrroopphhaassee Metaphase AAnnaapphhaassee
LLaattee AAnnaapphhaassee TTeelloopphhaassee TTeelloopphhaassee &
CCyyttookkiinneessiiss
??
?? ?? ??
?? ?? ??

100. 114
LLooccaattee tthhee FFoouurr MMiittoottiicc
SSttaaggeess iinn PPllaannttss
MMeettaapphhaassee
PPrroopphhaassee
AAnnaapphhaassee
TTeelloopphhaassee

101. QQuueessttiioonn::
4. The scientist draws some of the cells that
have been observed. In which stage of the
cell cycle are the cells shown below? (4)
Cell A: metaphase
Cell B: interphase
Cell C: anaphase
Cell D: prophase

102. 10. In humans, each cell (except sex cells) has how many chromosomes? ______
11. After mitosis, how many daughter cells are produced? _______
12. After mitosis (in a human cell), each daughter cell has how many chromosomes? _____
13. How many phases are in MITOSIS? ___________
14. Which phase of the cell cycle is the longest? _________
15. During which phase does cytokinesis begin? __________

103. Uncontrolled Mitosis
Cell ddiivviissiioonn iiss nnoorrmmaallllyy
ccoonnttrroolllleedd
IIff mmiittoossiiss iiss nnoott
ccoonnttrroolllleedd,, uunnlliimmiitteedd cceellll
ddiivviissiioonn ooccccuurrss ccaauussiinngg
ccaanncceerroouuss ttuummoorrss..
CCaanncceerr cceellllss
CCaanncceerr == ggeenneettiicc
ddiisseeaassee ccaauusseedd bbyy
uunnccoonnttrroolllleedd mmiittoossiiss
CCaanncceerr == ggeenneettiicc
ddiisseeaassee ccaauusseedd bbyy
uunnccoonnttrroolllleedd mmiittoossiiss
dduuee ttoo sseevveerree
ddiissrruuppttiioonn iinn tthhee
mmeecchhaanniissmm tthhaatt
ccoonnttrroollss cceellll ccyyccllee
dduuee ttoo sseevveerree
ddiissrruuppttiioonn iinn tthhee
mmeecchhaanniissmm tthhaatt
ccoonnttrroollss cceellll ccyyccllee

104. • IIff tthhee aabbnnoorrmmaall
cceellllss rreemmaaiinn aatt tthhee
oorriiggiinnaattiinngg ssiittee,,
tthhee lluummpp iiss ccaalllleedd
aa bbeenniiggnn ttuummoorr..
• ccaann bbee rreemmoovveedd bbyy
ssuurrggeerryy..
• IIff tthhee aabbnnoorrmmaall
cceellllss rreemmaaiinn aatt tthhee
oorriiggiinnaattiinngg ssiittee,,
tthhee lluummpp iiss ccaalllleedd
aa bbeenniiggnn ttuummoorr..
• ccaann bbee rreemmoovveedd bbyy
ssuurrggeerryy..
• IInn aa mmaalliiggnnaanntt ttuummoorr,,
tthhee cceellllss lleeaavvee tthhee
oorriiggiinnaall ssiittee..
• aarree ccaarrrriieedd bbyy tthhee
bblloooodd aanndd llyymmpphh ssyysstteemm
ttoo ootthheerr ttiissssuueess,, aanndd
ssttaarrtt mmoorree ttuummoorrss..
• IInn aa mmaalliiggnnaanntt ttuummoorr,,
tthhee cceellllss lleeaavvee tthhee
oorriiggiinnaall ssiittee..
• aarree ccaarrrriieedd bbyy tthhee
bblloooodd aanndd llyymmpphh ssyysstteemm
ttoo ootthheerr ttiissssuueess,, aanndd
ssttaarrtt mmoorree ttuummoorrss..

105. APPLICATION OF KNOWLEDGE
ON MITOSIS
IN CLONING

106. Cloning Dolly
1997 - 2003
(Roslin Institute http://www.roslin.ac.uk/library/)
BBoorrnn iinn SSccoottllaanndd,
DDoollllyy wwaass tthhee
ffiirrsstt mmaammmmaall ttoo
bbee cclloonneedd ((119977))
TThhiiss sshhoowweedd tthhaatt
DDNNAA iinn aadduulltt cceellllss
ccaann bbee rree--ssttaarrtteedd

107. Cloning an organism

108. Cloned animals:
(Reproductive Cloning)
First cloned rabbit
by Chinese scientists
First cloned horse
by Italian Scientists
Snuppy: first cloned dog
from South Korea.
CC “CopyCat”
First cloned cat
from Texas.
Ralph: The first cloned
rat by French scientists

109. Tissue Culture
• used to produce clones
of a plant
• More identical plants
produced in a short
time.

110. Genetically Engineering
• Involves the insertion of DNA from one organism
into another OR modification of an organism’s
DNA in order to achieve a desired trait.
+ A strawberry
= resistant to frost
4 5
Arctic fish DNA strawberry

111. The Benefits of Genetic
Engineering
1. Human Insulin
2. Crops with herbicide resistance
3. Crops with virus resistance
4. Crops that are drought tolerant
5. Control the ripening of fruits
6. Crops with increased nutrition
7. Milk production in cows with
hormones

112. Disadvantages of Cloning
• No variation
• Same level of resistance to diseases or
pests
• Danger: Entire population of clones could
be eliminated if not resistant to new threat.

113. WITH CREDITS TO
DR MARTHESE AZZOPARDI

115. CCoollcchhiicciinnee
 Is made from autumn
crocus (Colchicum
autumnale) - poisonous
Added to actively dividing
cells to inhibit spindle
formation

116. Chromatid pairs remain in their metaphase
positions
This technique enables the number and
structure of chromosomes to be examined
under the microscope

117. The DNA content of the cell as shown below
is 10 units.
What will the DNA content be at the end of
mitosis?

118. DNA content and mitosis

119. DNA Content
DNA duplication
during interphase
Mitosis
20 units
40 units
20 units 20 units