10 min 10 question quiz
Post on 16-Jan-2016
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Do now: List the phases of the cell cycle
The Cell CycleComposed of 4 phases
G1(gap 1)S (DNA replication/Synthesis)G2 (gap 2)M (Mitosis and cytokinesis)
Interphase
Mitotic phase
Aim: What is the cell cycle?
G1 and G2Phases of cell growth, differentiation (modification
of cell to perform particular functions) and cell activity.
Aim: What is the cell cycle
S (DNA synthesis)Copies of DNA needed for cell division are
made in this phase. (DNA Replication)
Aim: What is the cell cycle
G0Cells that stop growing and dividing leave the
cell cycle and enter this phaseDo you know of any cells that stop dividing?Http://www.youtube.com/watch?v=P9ngTBG2e0EThey are still metabolically active (continue
doing all the chemical processes they need to survive) and viable (alive and useful)
Aim: What is the cell cycle
M (Mitosis and Cytokinesis)Mitosis-nuclear division
Cytokinesis-division of the cell’s cytoplasm. At the end of mitosis and during cytokineses chromosomes uncoil and DNA starts directing protein synthesis
Aim: What is the cell cycle
Continual proliferationIf a cell that should be in G0 is not in G0 goes
into continual proliferationThis means that it continues to grow and
divide uncontrollablyThis can lead to cancer.
Aim: What is the cell cycle
Initiation of MitosisA protein complex called MPF (mitosis promoting
factor) initiates mitosis in the cell cycleMPF is a protein factor made of 2 proteins: an
oscillating protein (constantly increasing and decreasing in amount) called Cyclin B and a constant
kinase called CDC2.A kinase is an enzyme that ads a phosphate to a
protein in a process called phosphorylation.
Because CDC2 only works when Cyclin B is present it is referred to as a Cyclin Dependant Kinase
Aim: What is the cell cycle
P
1. CDC2 remains constantly and inactive in the cell
2. There is an increase of Cyclin B
3. Cyclin B phosphorylates
CDC2(adds 2 phosphates)
Aim: What is the cell cycle
Steps to initiate mitosis1. CDC2 remains constantly and inactive in the
cell2. There is an increase of Cyclin B
3. Cyclin B phosphorylates CDC2(adds 2 phosphates)
4. Another kinase then removes one of the phosphates
5. Mitosis starts
6. Cyclin B is degraded and CDC2 becomes inactive again
Aim: What is the cell cycle
P
1. CDC2 remains constantly and inactive in the cell
2. There is an increase of Cyclin B
3. Cyclin B phosphorylates
CDC2(adds 2 phosphates)
4. Another kinase then removes one of the phosphates
5. Mitosis starts6. Cyclin B is degraded
and CDC2 becomes inactive againAim: What is the cell cycle
Cell Cycle Check PointsMake sure that events have been completed before commencing the next phase.There are 3 major checkpoints1.G1/S checkpoint-checks for cell size and damaged DNA.
S-phase promoting factor is a protein used at this checkpoint to prepare DNA for replication.
Aim: What is the cell cycle
Cell Cycle Check Points2. G2/M checkpoint-checks for proper and
complete DNA synthesis/replication and damaged DNA.
3. M checkpoint-checks spindle fibers formation and attachment to chromatids
Aim: What is the cell cycle
G2/M
Aim: What is the cell cycle
ApoptosisG1/S check detects too much DNA damage
the cell might selfdestruct.Apoptosis is programed cell deathHowever, if among the damaged DNA is the
p53 the call cannot selfdestruct ensuring cancer.
This gene has been linked to colon, breast, lung and many other cancers.
Aim: What is the cell cycle
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