ONS/ONCC Chemotherapy
Immunotherapy Certificate
The Normal Cell Cycle
-The cell cycle refers to the ordered seres of processes of DNA replication and mitosis, or
cell division
-Cell nucleus regulates these processes by gathering and processing complexes molecular
information
Interphase and Mitotic Phase
Cell division produces two identical cells through these two major phases
During interphase:
Cell grows and DNA is replicated through the following three steps:
1: First growth phase (G1 or first gap)
2: Synthesis phase (S phase)
3:Mitotic Phase (M phase)
First Growth Phase (G1 or first gap)
-cells increase in size
-reproduce RNA
-"quality assurance" test that the cell will be ready to synthesis DNA
-Length of time is variable, can be from hours to days
Synthesis Phase (S phase)
-DNA replicates
-Results in the formation of identical pairs of DNA (chromatids)
-which are attached a t the centromere
-lasts 2-10 hours
,Mitotic Phase (M phase)
-Replicated chromosomes are aligned, separated, and move into 2 new, identical daughter
cells
-takes about 30-60 minutes
Major points of cell regulation are entry and exit from
-G1 checkpoint
-S Phase
-G2 checkpoint
-M phase
Restriction Point
-The transition from the resting phase into an actively dividing phase (G0-G1) is a point
where cellular transformation can occur
-During this time, cells pass through a transition phase known as a restriction point
-Extracellular growth factors trigger reentry into G1, and GF are required to send the cells
past the restriction point, or the point of no return
G0 Phase (resting phase)
-After mitosis, cells may enter back into the G1 phase or go into a resting phase, known as
G0
-Most cells in the human body reside in G0
-Exceptions to this are those that are (Resting in G0 phase) - what are other exceptions?
-Exceptions to this are those that are metabollically active, such as
-granulocytes
-and the epithelium of the GI tract
Cell Cycling Time
Amount of time from mitosis to mitosis
Check points in the Cell Cycle: Keeping it All Under Control
-The cell cycle is carefully controlled through a series of checkpoints
-Variation in duplication or distribution of chromosomes during cell division can alter the
genetic information passed on to daughter cells, leading to cellular dysfunction and disease,
such as cancer
-These checkpoints monitor for DNA integrity and control progression through mitosis
Progression through the cell cycle is controlled through two proteins:
1. cyclines (D, E, A, B)
2. Cyclin-dependent kinases (CDKs)
-Cyclin-CDK complex allows the cell to progress through each phase of the cell cycle
Locations of proteins Cyclins (D, E, A, B) and CDKs
-(G0-G1) : Cyclin D and CDK 4/6
-Early S: Cyclin E and CDK 1/2
-Late S: Cyclin A and CDK 1/2
-G2: CDK 1/2 and cyclin A
-Before M: CDK 1 and Cyclin B
Inhibitory proteins
-prevent progression of the cycle when DNA damage is detected
-An example of an inhibitory protein is p53 (AKA TP53)
DNA Damage Checkpoints
-If DNA damage is present, cells are programmed to stop dividing or undergo apoptosis
(programmed cell death)
-The retinoblastoma protein (Rb), p53, and p21 are some of the most well-understood
inhibitory proteins (IP)
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