Chapter 18 -> The Cell Division Cycle Flashcards
All living organisms are products of repeated rounds of cell ______ and _______
Growth, Division
What is the Cell Cycle?
Cycle of duplication and division
Universal truths of the cell cycle
- Cells must copy and pass on their _________ to the next generation of cells
- DNA in chromosomes must be ________
- Replicated chromosomes must be ________ into the two daughter cells
Genes
Duplicated
Seperated
What are the three overview steps of the cell cycle?
1) Cell Growth and Duplication
2) Chromosomes Segregation
3) Cell Division
Why is a fly’s cell cycle faster than a bacterial cell cycle?
The number of Origins of Replications is greater in the fly than the bacteria
The eukaryotic Cell Cycle is divided into what 4 phases?
M Phase
G1 Phase
S Phase
G2 Phase
What occurs during the M Phase of the cell cycle?
Nucleus divides, Cytoplasm divides, and Cell Splits into 2 (cytokinesis)
Interphase constitutes what phases of the cell?
What occurs during Interphase?
G1, G2, and S Phases
Cell increases in size
What occurs during the S phase of Interphase?
DNA is replicated
S phase is in between the G1 and G2 resting phases
What occurs during G1 Phase of Interphase?
Completion of M phase to beginning of S phase
Sort of a gap/growth period in the cell cycle
What occurs during G1 Phase of Interphase?
Completion of M phase to beginning of S phase
Sort of a gap/growth period in the cell cycle
What is the main purpose of G1 and G2 phases of the cell cycle?
Allows for time for cell to grow and duplicate organelles
A central control system triggers the major processes of the cell cycle
When this mechanism breaks, what occurs?
Cancer
The central control system in the cell cycle is regulated at certain points by _________ from the processes
Feedback
Two important checkpoints in G1 and G2
G1 checkpoint allows cell to confirm that…
G2 checkpoint ensures that cells don’t enter mitosis until damaged ______ is repaired and DNA replication is complete
environment is favorable for proliferation and DNA is intact before going to S Phase
DNA
What are the two types of machinery that are involved in cell division?
How does the cell cycle control system control all of this?
Manufacturing new components of growing cell
Hauling components into correct places
Switches the machinery on and off at correct times throughout cycle
The cell cycle control system depends on ___________
The system can cyclically activate then deactivate key proteins that initiate or regulate __________ (3 things)
Cyclically activated protein kinases
DNA replication, Mitosis, Cytokinesis
____________ and ____________ are common ways for cells to switch the activity of proteins on or off
Phosphorylation, Dephosphorylation
What do protein kinases do?
Transfer P group from ATP to a protein changing the conformation of the protein
What do protein phospatases do?
Remove P group
Cyclin-dependent kinases rely on a set of proteins called _________ to switch them on and off at the appropriate time
Cyclins have to bind to the cell cycle kinases before the kinases can become ________
Cyclins
Activated
Cyclin dependent protein kinases are regulated by the accumulation and destruction of ________
Cyclins
Cyclin Example: M-cyclin (M-CDK Complex)
synthesis of M-cyclin starts after cell division, continues through interphase and continues to rise in concentration
This times the onset of ________, cells entering M-phase
After, M-cyclin is rapidly eliminated and cells then exits the _ phase
Mitosis
M
M-CDK Complex Summary
Flooding of M-cyclin causes _________ to becomes active and ready to phosphorylate key proteins that push the cell into M-phase
For M-CDK to be active and at its max, it has to be ___________ at certain sites and _____________ at other sites
Kinases
Phosphorylated, Dephosphorylated
At the end of M-phase, a fall in ____-______ concentration occurs, causing _________ to tag protein then demolish it
to control tagging of m-cyclin, a protein complex called the ______ ________ _______ adds Ubiquitin tags to the cyclin
This complex is only switched on late in M-phase
m-cyclin, Ubiquitins
Anaphase Promoting Complex
Universal cyclin property
the concentration of each type of cyclin rises ________ then falls ________ as a result of Ubi degradation
slowly, rapidly
Summary of M-Cyclin Control Mechanism
1) M-cyclin concentration _______ throughout interphase interacting with kinases, forming ____-______ complexes, but they are not yet active
2) When appropriate concentration is reached, ______________ step activates CDK-Cyclin complex and pushed cell into mitosis
3) Late in the M-phase, _________ causes M-cycliin to be tagged for degradation by ________
4) M-cyclin degraded complex is now inactive and cell can move on from mitosis
1) Increases, CDK-Cyclin
2) dephosphorylation
3) APC, Ubiquitin Tags
DNA damage causes an increase in concentration and activity of _______
P53 then activates the production of ________
P21 binds to G1/S-CDK and S-CDK preventing cell from going into ____ phase
P53
P21
S
What happens if p53 is missing or defective
Replication of damaged DNA occurs, leading to production of cancerous cells
Mutations in p53 gene are found in about ______ of all human cancers
Half
Apoptosis
The number of cells in an organism are controlled by rates of cell division and rates of cell death
Steps of Apoptosis
1) The cells shrinks and condenses
2) ________ collapses
3) Nuclear envelope dissasmebles
4) Nuclear DNA breaks into _________
5) Cell surface is altered -> attracts ________ cells
6) Cell engulfs and splits contents
Cytoskeleton, Phagocytic
What is cell necrosis?
The spilling of cell contents onto neighboring cells
What proteases enzyme carries out apoptosis by cutting up other proteins?
Activated caspases cleave and activate other members of the family resulting in a cascade
Once a cell reaches a critical point along the path to destruction it cannot turn back
Caspases
Apoptosis Summary
1) occurs in developing or adult ________ where cells receive a signal to die
2) Process is controlled by the enzyme ______
3) Procaspases (the inactive form of a caspase) are activated by cleavage leading to the formation of ____________
4) This causes a caspase _________ cascade
5) Results in cytoskeleton, nuclear membrane, and DNA damage followed by _______
1) tissues
2) caspase
3) apoptosome
4) protein
5) phagocytosis
What does the myostatin gene do?
Causes everything to look buff as hell
Cyclin dependent protein kinases are regulated by the accumulation and destruction of ________
The cyclin that helps drive cells into m phase is called _______
The active complex that it forms with its CDK is called ______
Cyclins
M-Cyclin
M-CDK
M-CDK Complex Summary
Synthesis of M-cyclin starts after _______ and continues throughout interphase
M-cyclin accumulate, causing the onset of _______
It is then rapidly eliminated and cell exits M-Phase
Cell Division
Mitosis
The activity of CDKs is regulated by ___________ and ___________
Example: for M-CDK to be maximally active, it has to be phosphorylated at certain sites and dephosphorylated at other sites
*The removal of ____ group by a phosphatase is the final step that activates MCDK at the end of interphase
Phosphorylation and Dephosphorylation
P
Summary of M-Cyclin Control Mechanism
1) M-cyclin concentration increases throughout _______ all the time complexing with kinase to form _______________ complex, but is not active
2) When the appropriate concentration is reached, dephosphorylation by ______ activates CDK-Cyclin complex, pushing cell into mitosis
3) Late in M-Phase, _____ causes M-Cyclin to be tagged for degradation by ______
4) At end of mitosis, M-cyclin degraded CDK-Cyclin complex is therefore ________
5) Cell pushed from mitosis and the process begins again
1) Interphase, CDK-Cyclin
2) Wee1
3) APC, UBI
4) Inactive
