The Cell Cycle, Mitosis and Cytokinesis

1. Mr. Louis Alexiz C. Urbina, LPT, MCEd, MSc
Cellular Reproduction
The Cell Cycle, Mitosis and Cytokinesis

2. 1. Explain the importance of
mitosis and cell death during
development, growth, and
repair of the human body.
2. Describe the phases of the cell
cycle and what happens in each
phase.
3. Explain the relationship
between cancer and the cell
cycle
Learning Targets

3. Cellular Reproduction
Lesson Outline
I. The Cell Cycle
I.I. Interphase
• G1, S and G2
•M Stage
•Control of the Cell Cycle
I.II.Phases of Mitosis
•Prophase
•Metaphase
•Anaphase
•Telophase
•Cytokinesis
https://astrobiochem.
fi
les.wordpress.com/2018/09/pic.png?w=520

4. Introduction
Cell Growth and Division
• All living things grow by
producing more cells
• Cell division enables a
single cell to eventually
produce many cells,
allowing an organism to
grow and develop

5. Introduction
DNA Basics
•During the
fi
rst part of an
organism’s life, all cells
divide
•When adulthood is
reached, only speci
fi
c
cells (human blood and
skin cells) continue to
divide daily
http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/graphics/
nuc_to_bp.gif
•The nucleus is a
membrane bound
organelle that contains
the genetic information in
the form of chromatin
•When a cell divides,
chromatin
fi
bers are very
highly folded and become
visible in the light
microscope as
chromosomes.
•The DNA of chromatin is
wrapped around a complex
of histones making what
can appear in the electron
microscope as "beads on a
string" or nucleosome
•DNA or deoxyribonucleic acid
is a large molecule structured
from chains of repeating units
of the sugar deoxyribose and
phosphate linked to four
di
ff
erent bases abbreviated A,
T, G, and C.

6. Introduction
Chromosome Structure
https://1.bp.blogspot.com/-6RK2yHHrfQM/XI7EDi1yUAI/AAAAAAAAARw/
eGtf7yOqNOkBvcGqIMFk2H0u41lwhshQACLcBGAs/s1600/chromosome-and-chromatid.jpg

7. Introduction
The Cell Cycle
https://cdn1.byjus.com/wp-content/uploads/2020/01/Cell-cycle-phases-01.png
The cell cycle is an orderly
set of stages that take
place between the time a
eukaryotic cell divides and
the time the resulting
daughter cells also divide.

8. Interphase
G1 Stage
• cells are constantly
performing their
normal daily
functions, including
communicating with
other cells, secreting
substances, and
carrying out cellular
respiration
• increases in size,
doubles its organelle
Some cells, such as nerve and muscle cells,
typically do not complete the cell cycle and
are permanently arrested. These cells are said
to have entered a G0 stage
Mader (2010)

9. Interphase
S Stage
• DNA synthesis or
replication occurs
• 46 chromosomes to
92 chromatids
Mader (2010)

10. Interphase
G2 Stage
• cell synthesizes
proteins that will
assist cell division
• Make more
microtubules
Mader (2010)

11. Control of the Cell Cycle
Cell Cycle Checkpoints
• Apoptosis - programmed cell
death
• A signal is an agent that in
fl
uences
the activities of a cell
• Cyclins - internal signaling proteins
p53 RB
Mader (2010)

12. M Stage
Mitotic Stage
The cell divides into two
daughter cells along with equal
distribution of chromosomes
between the daughter cells
• This cell division stage
includes:
• mitosis (nuclear division)
and
• cytokinesis (division of
the cytoplasm)
Mader (2010)

13. Phases of Mitosis
https://www.expii.com/t/what-is-mitosis-de
fi
nition-overview-10158

14. Mader (2010)

15. Mader (2010)

16. Cytokinesis
• The cleavage furrow deepens
when a band of actin
fi
laments,
called the contractile ring, slowly
forms a circular constriction
between the two daughter cells.

17. 🔑 Key Points
The Cell Cycle
• Eukaryotic cells go through a cell cycle that includes (1) interphase and
(2) a mitotic stage that consists of mitosis and cytokinesis.
• Interphase is composed of three stages: G1 (growth) as certain organelles
double), S stage (synthesis), where the chromosomes are duplicated, and
G2 as the cell prepares to divide.
• Most cells of the body are no longer dividing and are said to be arrested in
a G0 state.
• Cell cycle checkpoints: G1, G2, and M checkpoint

18. 🔑 Key Points
Mitosis and Cytokinesis
• Prophase—The nucleolus disappears, the nuclear envelope fragments, and the
spindle forms between centrosomes. The chromosomes condense and become
visible under a light microscope.
• Pro-metaphase (late prophase)—The kinetochores of sister chromatids attach to
kinetochore spindle
fi
bers extending from opposite poles.
• Metaphase—The spindle is fully formed, and the duplicated chromosomes are
aligned at the metaphase plate.
• Anaphase—Sister chromatids separate, becoming daughter chromosomes that
move toward the poles.
• Telophase—Nuclear envelopes re-form, chromosomes begin changing back to
chromatin, the nucleoli reappear, and the spindle disappears.
• Cytokinesis in animal cells is a furrowing process that divides the cytoplasm.

19. Let’s Check
Choose the letter of the best answer.
The following graph shows how cellular DNA
content changes over the course of a typical
mitotic cell cycle in rapidly proliferating human
cells.
A. The amount of cellular DNA remains constant throughout the cell cycle.
B. The amount of cellular DNA is halved during interphase.
C. Human cells spend the same amount of time in M phase as they do in interphase.
D. Human cells spend the majority of the cell cycle in interphase.

20. Let’s Check
Choose the letter of the best answer.
The stage of the cell cycle where each chromosome is composed of two
chromatids in preparation for mitosis.
A. G1
B. S
C. M
D. G2

21. Let’s Check
Choose the letter of the best answer.
Which sequence of the cell cycle is common to eukaryotes?
A. G1 to G2 to S to M to Cytokinesis
B. G1 to S to G2 to M to Cytokinesis
C. G1 to M to G2 to S to Cytokinesis
D. G1 to M to S to G2 to Cytokinesis

22. Let’s Check
Choose the letter of the best answer.
The stage of the cell cycle where the cell is preparing
to begin DNA replication is called:
A. G1
B. G2
C. S
D. M

23. Let’s Check
Choose the letter of the best answer.
The proteins which complex with DNA producing the "beads on a string" or
nucleosomes are called:
A. Kinases
B. Retinoblastoma
C. Spindle Fibers
D. Histones

24. Let’s Check
Choose the letter of the best answer.
A student is examining an onion root tip cell under a microscope. Based on her
observations, the student proposes that the onion root tip cell has completed
interphase and is now in the
fi
rst phase of mitosis.
A. The cell’s chromosomes are aligned across the metaphase plate
B. Separated sister chromatid are being pulled towards opposite ends of the cell
C. Discrete chromosomes are scattered throughout the cell’s nucleus
D. The cell’s DNA is dispersed within the nucleus as chromatin

25. Let’s Check
Choose the letter of the best answer.
In response to critically low nutrient levels, yeast cells often enter into a
dormant, non-dividing state. This state allows yeast cells to
survive until nutrient levels are restored, at which point the
cells typically re-enter the cell cycle.
A. Transition from G1 to G0 phase
B. Transition from G0 to G1 phase
C. Transition to mitosis
D. Transition to meiosis

26. Let’s Check
Choose the letter of the best answer.
A mouse skin cell containing 40 chromosomes undergoes mitosis.
This process results in the formation of:
A. Four daughter nuclei, each with 20 chromosomes
B. Four daughter nuclei, each with 40 chromosomes
C. Two daughter nuclei, each with 20 chromosomes
D. Two daughter nuclei, each with 40 chromosomes

27. Let’s Check
Choose the letter of the best answer.
Which of the following statements is NOT true of mitosis?
A single nucleus gives rise to two identical daughter nuclei.
B.The daughter nuclei are genetically identical to the parent nucleus.
C.The centromeres divide at the onset of anaphase.
D.Homologous chromosomes synapse in prophase.

28. Let’s Check
Choose the letter of the best answer.
The sputum (
fl
uid coughed up from the lungs) of many smokers contain cells
with mutations (errors) in the genes for p53. The smoking induced mutations
appear to be an early signal showing that cancer of the lungs will follow.
What is the likely relationship between early p53 mutation
and the development of lung cancer?
A. p53 with a mutation directly stimulates the growth of cancer cells
B. mutations in p53 would prevent abnormal cells from dying by apoptosis
C. mutant p53 triggers the M phase of the cell cycle leading to abnormal cell division
D. p53 causes a cell to enter G0, blocking cell division

29. References
• Mader, S. (2010). Biology, tenth edition. McGraw-Hill Companies, Inc., Avenue
of the Americas, New York, NY
• https://www.genome.gov/genetics-glossary/Cell-Cycle
• https://rsscience.com/why-cell-division-is-important/
• https://byjus.com/neet/4-phases-of-cell-cycle/
• https://www.youtube.com/watch?v=VXLSTd_dlKg
• https://www.khanacademy.org/science/ap-biology/cell-communication-and-
cell-cycle/cell-cycle/a/phases-of-mitosis