Lesson 1: Foundations to Set the Stage –
Focusing on Cellular Structure and Function –
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 Phse (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) – -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
Cell cycle video and image –
http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation_
_how_the_cell_cycle_works.html
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)
- 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)
Inhibitory proteins p53 – -Levels of this IP regulate several important target genes
-Will increase when DNA damage is present
-Protects against inappropriate signal proliferation
-sometimes called the “suicide gene”
M Phase Checkpoints – When the cells prepare to divide, the chromosomes line up in
the mitotic spindle.
If the chromosomes are not properly aligned, division is not allowed to continue
Immunity –
Cells of the Immune System –
Pluripotent Stem Cell – -The cells of the immune system are created in the bome
marrow from what is know as a _
-A stem cell that can differentiate into any cell type except for extraembryotic tissue,
does not yet have a function
Myeolid Precursor Cells – Mature into:
-RBCS
-Plts
-WBCs (Granulocytes)
Lymphoid Precursor Cells – Mature into:
-Specialized WBCs called lymphocytes (Agranulocytes)
Lines of Defense: The Immune System’s Response to Attack – Consists of 2 types of
immunity:
1: Innate
2: Adaptive
Innate Immunity – -First line of defense against a pathogen
-Does not retain memory of the entity
-Involves the following:
(skin, mucous membranes, and normal flora of the skin and gut)
(Cellular components such as phagocytes, natural killer cells, granulocytes, and
macrophages) - Phagocytes
- Natural Killer Cells
- Granulocytes