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Lesson 1: Foundations to Set the Stage
Focusing on Cellular Structure and Function
-The cell cycle refers to the ordered seres of processes of DNA
replication and mitosis, or cell division
The Normal Cell Cycle
-Cell nucleus regulates these processes by gathering and pro-
cessing complexes molecular information
Interphase and Mitotic Phase Cell division produces two identical cells through these two major
phases
Cell grows and DNA is replicated through the following three steps:
1: First growth phase (G1 or first gap)
During interphase:
2: Synthesis phase (S phase)
3:Mitotic Phse (M phase)
-cells increase in size
-reproduce RNA
First Growth Phase (G1 or first gap)
-"quality assurance" test that the cell will be ready to synthesis
DNA
-Length of time is variable, can be from hours to days
-DNA replicates
-Results in the formation of identical pairs of DNA (chromatids)
Synthesis Phase (S phase)
-which are attached a t the centromere
-lasts 2-10 hours
-Replicated chromosomes are aligned, separated, and move into
2 new, identical daughter cells
Mitotic Phase (M phase)
-takes about 30-60 minutes
-G1 checkpoint
-S Phase
Major points of cell regulation are entry and exit from
-G2 checkpoint
-M phase
-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
Restriction Point 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
-After mitosis, cells may enter back into the G1 phase or go into a
resting phase, known as G0
G0 Phase (resting phase)
-Most cells in the human body reside in G0
-Exceptions to this are those that are metabollically active, such
as
, ONS/ONCC CHEMOTHERAPY IMMUNOTHERAPY CERTIFICATE ACTUAL EXAM
QUESTIONS AND WELL DETAILED ANSWERS LATEST UPDATE|WELL STRUCTURED|
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-granulocytes
-Exceptions to this are those that are (Resting in G0 phase)
-and the epithelium of the GI tract
Cell Cycling Time Amount of time from mitosis to mitosis
http://highered.mheducation.com/sites/0072495855/stu-
Cell cycle video and image dent_view0/chapter2/animation how_the_cell_cy-
cle_works.html
-The cell cycle is carefully controlled through a series of check-
points
-Variation in duplication or distribution of chromosomes during cell
Check points in the Cell Cycle: Keeping it All Under Control 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 progres-
sion through mitosis
1. cyclines (D, E, A, B)
Progression through the cell cycle is controlled through two pro- 2. Cyclin-dependent kinases (CDKs)
teins:
-Cyclin-CDK complex allows the cell to progress through each
phase of the cell cycle
-(G0-G1) : Cyclin D and CDK 4/6
-Early S: Cyclin E and CDK 1/2
Locations of proteins Cyclins (D, E, A, B) and CDKs -Late S: Cyclin A and CDK 1/2
-G2: CDK 1/2 and cyclin A
-Before M: CDK 1 and Cyclin B
-prevent progression of the cycle when DNA damage is detected
Inhibitory proteins
-An example of an inhibitory protein is p53 (AKA TP53)
-If DNA damage is present, cells are programmed to stop dividing
or undergo apoptosis (programmed cell death)
DNA Damage Checkpoints
-The retinoblastoma protein (Rb), p53, and p21 are some of the
most well-understood inhibitory proteins (IP)
-Levels of this IP regulate several important target genes
-Will increase when DNA damage is present
Inhibitory proteins p53
-Protects against inappropriate signal proliferation
-sometimes called the "suicide gene"
When the cells prepare to divide, the chromosomes line up in the
mitotic spindle.
M Phase Checkpoints
If the chromosomes are not properly aligned, division is not al-
lowed to continue
Immunity
Cells of the Immune System
-The cells of the immune system are created in the bome marrow
from what is know as a
Pluripotent Stem Cell
-A stem cell that can differentiate into any cell type except for
extraembryotic tissue, does not yet have a function