Cell cycle & Deathfor MLT students

1. MODULE 1
TOPIC
CELL CYCLE & CELL DEATH

2. Course outcomes
On completion of this lecture the student will be
able to:
• Demonstrate cell & Cell organelles , Tissues, &
Organ systems of Human body

3. Learning Objectives
After this lesson, students will be able to:
1. Describe the role of chromosomes in cell
division.
2. Name the main events of the cell cycle.
3. Describe what happens during the four
stages of mitosis.
4. Describe the process of cytokinesis.

4. Learning Objectives
After this lesson, students will be able to:
1. Understand the functions of cell death in
development.
2. Provide specific examples of the roles of cell
death in development.
3. Understand some of the tissue interactions
that regulate developmental cell death.
4. Describe the basic molecular mechanisms
that underlie the cell death process.

5. A. Contents – Cell Cycle
1. Introduction to cell cycle
2. Stages of cell cycle
3. Phases of M phase
4. Prophase
5. Prometaphase
6. Metaphase
7. Anaphase
8. Telophase
9. Cytokinisis

6. B. Contents – Cell death
• Introduction
• Types of cell death
• Mechanism of Apoptosis
• Mechanism of Necrosis
• Difference between Apoptosis And Necrosis
• Factors causing Apoptosis
• Factors causing Necrosis

7. What is cell cycle?
1. The cell cycle is a process in which a cell grows and divides to
create a copy of itself.
2. Some organisms reproduce through the cell cycle, and in complex
multicellular organisms, the cell cycle is used to allow the
organism to grow, and to replace cells as they grow worn out.
3. In animals, the whole cell cycle takes around 24 hours from start
to finish.
4. Some cells, such as skin cells, are constantly going through the cell
cycle, while other cells may divide rarely, if at all;
5. neurons, for example, dont grow and divide once they are
mature.

8. It’s not as simple as This!

9. Chromosomes
In eukaryotic cells, DNA is packaged into multiple chromosomes.
centromeresister
chromatids
supercoils
coils
histone
proteins
nucleosome
DNA
double
helix

10. Eukaryotic Cell Cycle
Eukaryotic cells have a more complex cell cycle than
prokaryotic cells.

12. M Phase
Cell division occurs during M phase.

13. M-Phase

14. Prophase
The nucleus condenses and chromosomes become visible.
The spindle begins to form.

15. Metaphase
Chromosomes line up at the center of the cell.
centrioles
centromere
chromosome
chromatid

16. Anaphase
Chromosomes move toward opposite poles.
individual
chromosomes

17. Telophase
The cell begins to divide into daughter cells.
nuclear envelopes
re-forming

18. Cytokinesis
pinches in the center to form two daughter cells.Cytoplasm

19. Mitosis Overview
List and describe the stages of mitosis.
Interphase
1
2
3
4
Cytokinesis Prophase
Metaphase
Anaphase
Telophase

22. • Cell cycle
• In both unicellular and multicellular eukaryotes, the cell reproduction is a
cyclic process of growth, nuclear division and usually cytoplasmic division
called cell cycle.
• Cell cycle is a series of macromolecular events that lead to cell division
and the production of two daughter cells, each
containing chromosomes identical with those of the parental cell.
• Two main molecular processes take place during the cell cycle are
duplication of parental chromosome during S phase and separation of
chromosome equally to daughter cell during M phase.
• In somatic cell, the cell cycle consists of following four phase;
• G1 (gap 1) phase
• S (synthesis) phase
• G2 (gap2) phase
• M (mitosis) phase
Lecture Material

23. 1. G1 (gap1) phase:
• 1. G1 (gap1) phase:
• The first stage of interphase is called the G1 phase (first gap) because, from a
microscopic aspect, little change is visible. However, during the G1 stage, the cell is
quite active at the biochemical level.
• It is characterized by a change in chromosome from condensed state to more extended
state and series of metabolic events that leads to initiation of DNA replication. During
G1 phase, chromatin fibres become slender, less coiled and fully extended and more
active for transcription. The transcription results in synthesis of RNAs (tRNA, mRNA and
rRNA) ad series of proteins molecules required for initiation of DNA replication.
• The length of G1 phase varies from cell to cell and also the length of G1 phase is more
than other three phase in cell cycle.
• G1 phase represents 25-40% of generation time of a cell.
• G1 phase is very significant phase of cell cycle as the cell grows and accumulates the
building blocks of chromosomal DNA and the associated proteins as well as sufficient
energy reserves to complete the task of replicating each chromosome.
• Within G1 phase there is a definite check point at which DNA synthesis is initiated and
once the biochemical events associated with that point have occurred cell proceeds
towards division.

24. 2. S (synthesis) phase:
• 2. S (synthesis) phase:
• The synthesis phase of interphase is biochemically a phase of active DNA synthesis
and histone synthesis.
• In the S phase, chromosome numbers doubles which is accomplished by DNA
replication and associated proteins. Although some of the histone protein
synthesis occurs in G1 phase, most of it is synthesized during S phase.
• DNA replication is semi conservative and discontinuous type which results in the
formation of identical pairs of DNA molecules.
• After doubling of chromosome, sister chromatids are still firmly attached to the
centromeric region.
• At the center of each animal cell, the centrosomes of animal cells are associated
with a pair of rod-like objects, the centrioles, which are at right angles to each
other. Centrioles help organize cell division. Centrioles are absent in plants and
most fungi.
• The centrosome (centriole) is also duplicated during the S phase. The two
centrosomes will give rise to the mitotic spindle, the apparatus that mediate the
movement of chromosomes during mitosis.

25. 3. Gap2 (gap2) phase:
• 3. Gap2 (gap2) phase:
• G2 phase follows S phase. This phase represents 10-25% of
generation time of cell.
• In G2 phase chromosome consists of two chromatids ie the
cell has twice the amount of DNA content.
• In the G2 phase, the cell restore its energy stores and
synthesizes proteins necessary for chromosome
manipulation.
• Some cell organelles are duplicated, and the cytoskeleton is
dismantled to provide resources for the mitotic phase.
• There may be additional cell growth during G2. The final
preparations for the mitotic phase must be completed
before the cell is able to enter the first stage of mitosis

26. 4. M (mitotic) phase:
• 4. M (mitotic) phase:
• M phase follows G2 phase. During this phase cell divides into two daughter cell
with equal distribution of chromosome among daughter cells. After M phase cell
enter into G1 phase and next cell cycle is repeated. However, some cell after
completion of mitosis do not enter into G1 phase, those cell are referred as G0
cells.
• M phase consists of following sub –phases;
• During prophase, the nucleus disappears, spindle fibers form, and DNA condenses
into chromosomes (sister chromatids ).
• During metaphase, the sister chromatids align along the equator of the cell by
attaching their centromeres to the spindle fibers.
• During anaphase, sister chromatids are separated at the centromere and are
pulled towards opposite poles of the cell by the mitotic spindle.
• During telophase, chromosomes arrive at opposite poles and unwind into thin
strands of DNA, the spindle fibers disappear, and the nuclear membrane
reappears.
• Cytokinesis is the actual splitting of the cell membrane; animal cells pinch apart,
while plant cells form a cell plate that becomes the new cell wall.
• Cells enter the G0 (inactive) phase after they exit the cell cycle when they are not
actively preparing to divide; some cells remain in G0 phase permanently.

27. Cell death

32. Functional Significance of Apoptosis
• The purpose of apoptosis is to remove unwanted
cells without causing any stress or damage to
the neighboring cells. The functional significance
of apoptosis:
• 1. Plays a vital role in cellular homeostasis. About
10 million cells are produced everyday in human
body by mitosis An equal number of cells die by
apoptosis.
• This helps in cellular homeostasis
2. Useful for removal of a cell that is damaged
beyond repair by a virus or a toxin
• 3. An essential event during the development and
in adult stage.

43. Apoptotic Process
• Cell shows sequence of characteristic morphological
changes during apoptosis, viz.:
1. Activated caspases digest the proteins of cytoskeleton
and the cell shrinks and becomes round
2. Because of shrinkage, the cell losses the contact with
neighboring cells or surrounding matrix
3. Chromatin in the nucleus undergoes degradation

44. 4. Nuclear membrane becomes discontinuous and the
DNA inside nucleus is cleaved into small fragments
5. Following the degradation of DNA, the nucleus
breaks into many discrete nucleosomal units, which are
also called chromatin bodies
6. Cell membrane breaks and shows bubbled
appearance
7. Finally, the cell breaks into several fragments
containing intracellular materials including chromatin
bodies and organelles of the cell. Such cellular
fragments are called vesicles or apoptotic bodies
8. Apoptotic bodies are engulfed by phagocytes and
dendritic cells.

45. 2. Autoimmune lymphoproliferative syndrome (ALPS).

46. Necrosis

51. Causes of Necrosis

57. Reference
• https://www.google.com/search?biw=1164&bih=
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QCQ&q=tissues+reaction+to+necrosis+&oq=tissu
es+reaction+to+necrosis+&gs_l=img.3...396368.4
13888..414766...9.0..0.243.6294.1j30j5......0....1..
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zQD5IQ4dUDCAY&uact=5#imgrc=mu40nNidSSs-
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58. Material
• https://drive.google.com/open?id=1--RE-
2a__GmqnmecYN_S3PIIrT9cIriw
• www.bscmltonline.ga

59. Youtube videos
• https://www.youtube.com/watch?v=xsrH050
wnIA
• https://www.youtube.com/watch?v=1vaEVcM
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