Class XI, Unit III

1. Chapter-10
CELL CYCLE AND CELL
DIVISION
Presented by
B.Prabhakar
Principal
JNV. Panchmahal (Guj)

2. Formation of zygote

3. Zygote to foetus

7. Chromosome number
Fruit fly 8 Guinea Pig 16
Dove 16 Snail 24
Earthworm 36 Tibetan fox 36
Cat 38 Pig 38
Mouse 40 Rat 42
Rabbit 44 Syrian hamster 44
Hare 46 Human 46
Gorilla 48 Sheep 54
Elephant 56 Cow 60
Donkey 62 Horse 64
Dog 78 Chicken 78
Carp 104

9. Cell cycle

10. Phases of cell cycle
• 1. Interphase
• 2 Mitosis

11. Interphase
• It is devided into three
phages
• 1.G1 phase
• 2.S phase
• 3.G2 phase

12. Interphase

13. GI phase
• Cell grows in its size due to the synthesis
of proteins

14. •Centriole undergoes replication

15. S phase
During S phase DNA undergoes replication & each
DNA molecule forms two DNA molecules

16. Synthetic phase
• Each chromosome has single DNA.
During S phase DNA undergoes
replication & each DNA molecule forms
two DNA molecules
• Centriole undergoes replication
• There are the changes in animal cells

17. Chromatin at interphase

19. Events in the S phase in plants
• Only DNA replication takes place

20. G2 PHASE
• Proteins are synthesized in
preparation for mitosis

21. Mitosis
• It has two steps
• 1.Karyokinensis
• It is the division of nucleus
• 2.Cytokinensis
• It is the division of the cytoplasm

22. karyokinensis
• It has four phases
• 1. Prophase
• 2. Metaphase
• 3. Anaphase
• 4. Telophase

23. Prophase
1.Condensation of chromatin into
Compact chromosomes .
Each chromosome has two
chromatids,which are attached at the
centromere
2.Centrioles move towards the opposite
poles & initiation of the formation of the
mitotic spindle
3. At the end of the prophase nucleolus,
nuclear membrane disappear

25. Events in prophase
• 1.Condensation of chromatin into
Compact chromosomes .
Each chromosome has two
chromatids,which are attached at the
centromere
• 2.Centrioles move towards the opposite
poles & initiation of the formation of the
mitotic spindle
3. At the end of the prophase nucleolus,
nuclear membrane disappear

28. centromere

29. kinetochore
These are the small disc shaped structures at the
surface of the centromere
These structures serve as the sites of the
attachment of spindle fibers to the chromosomes
centromere

30. Key features of Metaphase
• Chromosomes are spread through out
the cytoplasm of the cell due to the
disintegration of the nuclear membrane
• Condensation of the chromosomes is
completed & they can be clearly seen
under the microscope
• Chromosomes move towards center of
the cell &they lie at the equatorial plate

31. Metaphase plate
• The plane
alignment of the
chromosomes at
metaphase is
referred as
metaphase plate

33. Centromere split &chromatids
separate
Chromatids move to opposite poles

34. Telophase
Nucleolus
Chromosomal clusters are seen at opposite poles
Nuclear envelop assembles around the
chromosomal clusters
Nucleolus reappears

40. Division of cytoplasm

41. Find out the correct sequence of different
stages of mitosis

42. Correct sequence

43. Questions
• Q1.Generally cell has single nucleus.Why some cells
have many nuclei?
• A.Nuclear division is not followed by cytoplasmic
division
• Q2.Human cell which is undergoing mitosis has 46
chromosomes. How many chromosomes will the cell
have at GIphase, after S phase,after M phase
• A. In all phases 46 chromosomes
• Q3 A cell has 14 DNA molecules. How many DNA
molecules does the cell consist in G1phase,G2 phase
respectively
• A. GI phase- 14
• G2 phase -28