https://youtu.be/DUFYRBALx94 video lecture link 🔗 This lecture explains the cell cycle checkpoints in cell division. Cell cycle checkpoints are really important stages of the cell cycle that helps a cell regulate the cell cycle and to cause the cell to live or die based on the modification of the cell cycle pathways. Stay tuned to this video lecture to understand the answers to the following questions - What is a cell cycle checkpoint? How does the cell cycle checkpoint work? What are the different cell cycle checkpoints? How did cell cycle checkpoints work? Cell cycle checkpoint regulation? Regulation of the cell cycle by the cell cycle checkpoint.

1. The dream of every cell is to becme
two cells.
G2 check
G1 check
G2 check
S check

2. Contents
• What is cell cycle.
• Phases of cell cycl.
• Cell Cycle checkpoints.
• Regulators of cell cycle.
• Positive and negative
regulators of cell cycle.

3. What is Cell cycle?
A cell cycle is a series of events
that result in cell division.
• Cell growth
• Duplication of genetic
material
• Cell division.

4. CELL
CYCLE
Interphase
˃90% of total
time of cell cycle
•1. Cell
growth
•2. DNA
replication
Cytokines
is
M Phase
˂10time of cell
cycle
% of total
Cell division
Phases of cell cycle

5. The stage of the cell cycle when a cell is preparing itself to
duplicate.
M phase: is the period of actual nuclear and cell division during which the
duplicated chromosomes are divided equally between two progeny cells.

6. Cell Cycle checkpoints
• To ensure the proper division of cell, there are control mechanisms.
• They prevent cell cycle progression at specific point, allowing verification of
necessary phase processes and Repair of DNA damage.
• In eukaryotic cell there are 3 main checkpoints that control cell cycle:
– G1 checkpoint.
– G2 checkpoint
– M checkpoint/spindle checkpoint

7. G1 checkpoint
• A cell checks whether the internal and
external conditions are right for division
• Factors that cell might assess:
– Size,
– Nutrients,
– Molecular signals,
– DNA integrity.
If cell doesn’t get the go-ahead cues it needs, it
may leave the cell cycle and enter a resting
state called G0 phase.
Some cells stay permanently in G0 phase, while
others resume dividing if conditions improve.
G1
checks

8. • It makes sure that cell division goes smoothly.
• It checks:
– DNA integrity,: Is any of the DNA damaged?
– DNA replication: was the DNA completely copied
during S phase?
If errors or damages are detected, the cell will
cell will pause at the G2 checkpoint to allow for
allow for repairs.
If the damage is irreversible, the cell may
may undergo apoptosis, or programmed cell
programmed cell death. This self-destruction
destruction mechanism ensures that damaged
damaged DNA is not passed on to daughter cells
daughter cells and is important in preventing
preventing cancer.
G2
checks
G2 checkpoint

9. • It occurs at metaphase.
• It checks whether all chromosomes are
properly attached to the spindle or not.
• Also governs the alignment of the
chromosomes and integrity of the
spindles.
If there are mistakes then it delays the cell in
entering into anaphase from metaphase.
M
checks
M checkpoint/spindle
checkpoint

10. Cell cycle regulators
• The cell cycle is regulated by:
– Cyclins,
– CDKs
1. are group group of proteins that control cell cycle activities. They
activate CDKs, which combine with the cyclins to modify certain proteins[that
regulate the cell cycle]. When cyclin finishes modifying proteins, it gets destroyed.
If cyclins malfunction, the cell cycle will go wrong, tumor could form.
CYCLINS

11. • There are 4 basic types of cyclins found in humans and
most of other eukaryotes:
– G1 cyclin
– G1/S cyclin
– S cyclin
– M cyclin.

12. Positive regulators
&
Negative regulators
Positive
regulators
Which control the
changes
necessary for cell
dividion:
Cyclins
Cyclin-dependent
kinase.
Negative
regulators
Which control the
positive
regulators
Rb proteins
P53 gene
Inhibitors of CDKs

13. Inhibitors of CDKs

14. Presented by
Ms. IQRA
IQ learning (YouTube channel)
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