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Fernand
Faculty of Farm
A
,BIOLOGY - CELL CYCLE 1-1-2025
Content
What is the normal state?
Cell cycle progression
Karyotype
Cell cycle
Cytokinesis
Chromosome
Distribution of chromosomes
Spermatocytes/spermatozoa
Strategies of different cell types
Phases of meiosis
Phases of mitosis
Formation of the poles for mitosis
Interface
External regulation of the cell cycle
Internal regulation of the cell cycle
Cellular senescence
Separation of chromosomes, assembly of the mitotic spindle
Cell types
, BIOLOGY - CELL CYCLE 1-1-2025
How does the cell cycle progress?
Through the successive activation and
inactivation of the various Cdkcyclin
complexes. To date, we know of four How the cell cycle is regulated
How the cell cycle is regulated
groups of these: externally?
internally?
1.Cdk-cyclin G1: they act by promoting the In a multicellular organism, the different
The cycle is regulated by the types of cells that divide do so in a
passage from G1 to S and in the progression of
phosphorylation and degradation of regulated manner. When this does not
the S phase.
proteins that form complexes. These occur, a particular group of overgrown
2.Cdk-cyclin G1/S: these complexes
complexes consist of two subunits: one cells can invade other tissues and thus
stimulate the cell to duplicate DNA.
regulatory and the other catalytic, that is, disrupt the normal organization and
with enzyme function. The regulatory functions of the organism. This occurs in
3.Cdk-cyclin S: They phosphorylate
subunit is calledcyclin because its thecancer.
and activate proteins involved in To the
concentration varies cyclically, following Certain external conditions, such as a
DNA replication. They act only once index
the changes the cell experiences during lack of nutrients, changes in
per cycle.
the cell cycle. The catalytic subunit is a temperature or pH, and the presence of
4.Cdk-cyclin M(mitosis-promoting
kinase, that is, an enzyme that catalyzes adjacent cells, can halt growth and
factor(MFP)): are formed during the
the transfer of a phosphate group from division, while certain hormones and
S and G phases2 but they remain
ATP to another molecule. Specifically, this growth factors can stimulate mitosis.
kinase is calledcyclin-dependent kinases inactive. Once DNA replication is
Growth factors typically bind to receptor
(CDK) because it only acts when complete, they become activated
proteins on target cells. This binding
associated with a cyclin. Phosphorylation, and induce condensation
produces a cascade of events within the
the transfer of the phosphate group, chromosomal decondensation, cell that triggers division.
activates certain proteins that, in turn, disintegration of the nuclear envelope,
trigger key cell cycle processes. assembly of the mitotic spindle, and
Depending on the cyclin involved, the Cdk- alignment of the chromosomes toward
cyclin complex will selectively the spindle poles. These complexes are
phosphorylate certain proteins. then degraded, allowing for chromosome
decondensation, restoration of the
nuclear envelope, and cytokinesis.
There are checkpoints that can stop or
continue the cycle but not turn it back.
Fernand
Faculty of Farm
A
,BIOLOGY - CELL CYCLE 1-1-2025
Content
What is the normal state?
Cell cycle progression
Karyotype
Cell cycle
Cytokinesis
Chromosome
Distribution of chromosomes
Spermatocytes/spermatozoa
Strategies of different cell types
Phases of meiosis
Phases of mitosis
Formation of the poles for mitosis
Interface
External regulation of the cell cycle
Internal regulation of the cell cycle
Cellular senescence
Separation of chromosomes, assembly of the mitotic spindle
Cell types
, BIOLOGY - CELL CYCLE 1-1-2025
How does the cell cycle progress?
Through the successive activation and
inactivation of the various Cdkcyclin
complexes. To date, we know of four How the cell cycle is regulated
How the cell cycle is regulated
groups of these: externally?
internally?
1.Cdk-cyclin G1: they act by promoting the In a multicellular organism, the different
The cycle is regulated by the types of cells that divide do so in a
passage from G1 to S and in the progression of
phosphorylation and degradation of regulated manner. When this does not
the S phase.
proteins that form complexes. These occur, a particular group of overgrown
2.Cdk-cyclin G1/S: these complexes
complexes consist of two subunits: one cells can invade other tissues and thus
stimulate the cell to duplicate DNA.
regulatory and the other catalytic, that is, disrupt the normal organization and
with enzyme function. The regulatory functions of the organism. This occurs in
3.Cdk-cyclin S: They phosphorylate
subunit is calledcyclin because its thecancer.
and activate proteins involved in To the
concentration varies cyclically, following Certain external conditions, such as a
DNA replication. They act only once index
the changes the cell experiences during lack of nutrients, changes in
per cycle.
the cell cycle. The catalytic subunit is a temperature or pH, and the presence of
4.Cdk-cyclin M(mitosis-promoting
kinase, that is, an enzyme that catalyzes adjacent cells, can halt growth and
factor(MFP)): are formed during the
the transfer of a phosphate group from division, while certain hormones and
S and G phases2 but they remain
ATP to another molecule. Specifically, this growth factors can stimulate mitosis.
kinase is calledcyclin-dependent kinases inactive. Once DNA replication is
Growth factors typically bind to receptor
(CDK) because it only acts when complete, they become activated
proteins on target cells. This binding
associated with a cyclin. Phosphorylation, and induce condensation
produces a cascade of events within the
the transfer of the phosphate group, chromosomal decondensation, cell that triggers division.
activates certain proteins that, in turn, disintegration of the nuclear envelope,
trigger key cell cycle processes. assembly of the mitotic spindle, and
Depending on the cyclin involved, the Cdk- alignment of the chromosomes toward
cyclin complex will selectively the spindle poles. These complexes are
phosphorylate certain proteins. then degraded, allowing for chromosome
decondensation, restoration of the
nuclear envelope, and cytokinesis.
There are checkpoints that can stop or
continue the cycle but not turn it back.
