Module 2 Control of the Cell Cycle Flashcards
The Tumor suppresors (3)
Retinoblastoma protein:
p53
p21
Typical cell cycle duration in Human Cell Maintained in culture
G1 (GAP 1)
G0
S (DNA Synthesis)
G2 (GAP 2)
M (Mitosis)
G1 (GAP 1)
5 hrs
G0
Variable lengths of time
S (DNA Synthesis)
7 hrs
G2 (GAP 2)
3 hrs
M (Mitosis)
1hr
Cell turnover:
early embryonic cells
epithelial cells
Specialized cells
early embryonic cells
Few hours
epithelial cells
Two to five days
Specialized cells
Entire human lifespan
Examples of specialized cells (2)
Cortical neurons
Cardiac muscle cells
Regulation by external events:
Both the ___ and ____of cell division are triggered by events external to the
cell when it is about to begin the replication process.
initiation
inhibition
Regulation by external events:
Whatever the source of the message, the cell receives the ____
a series of events within the cell allows it to proceed into ____
Moving forward from this ____ point, every parameter required during each cell cycle phase must be met or the cycle cannot progress.
signal
interphase
initiation
Regulation by external events:
The ____ of a nearby cell
The release of ____ hormones such as ____
____ of cells can also inhibit cell divisions
The ____ of the cell can also initiate cell division. This is because the cell becomes inefficient thanks to its ____ ratio wherein it needs to eventually divide.
Death
Growth-promoting hormones
HGH, Human Growth Hormone
Crowding
Size
Surface-to-Volume Ratio
____ are proteins that stimulate cell division
Growth Factors
Regulation by external events:
A lack of HGH or Human Growth Hormone can result in ____
An excess of HGH or Human Growth Hormone can result in ____
Dwarfism
Gigantism
Regulation by Internal Checkpoints:
Mistakes in the duplication or distribution of the chromosomes lead to ____ that may be passed forward to every new cell.
To prevent this, there are ____ that operate at _____.
Mutation
Internal Control Mechanisms
Three Main Cell Cycle Checkpoints
Regulation by Internal Checkpoints:
____ one of the several points in the eukaryotic cell cycle at which the progression of a cell to the next stage in the cycle can be halted until conditions are favorable
Location of these occur at the (3)
Checkpoint
End of G1
G2/M transition
During Metaphase
Regulation by Internal Checkpoints:
The integrity of the DNA is assessed at the ___
Proper _____ is assessed at the ____
Attachment of each ____ to a _____ is assesed at the ____
G1 checkpoint
chromosome duplication
G2 Checkpoint
Kinetochore
Spindle Fiber
M checkpoint
G1 checkpoint:
Also called ____(in yeast) determines whether all conditions are favorable for cell division to proceed
It is a point where the cell ____ to the cell division process
Restriction point
Irreversibly commits
G1 checkpoint:
Checks the following:
Adequate ___ and ___
Check for ___ at the G1 checkpoint which is then regulated by the ___ protein causing ____
Protein reserves and cell size
Genomic DNA damage
p53 protein
Apoptosis
G1 checkpoint:
If failed to meet the conditions, the cell cannot fo into the ____
The cell can halt the cycle and attempt tor emedy the condition or it can advance into ___ and await when conditions improve
S phase
G0 Phase
G2 checkpoint:
Bars entry into the ____ phase if certain conditions are not met.
This checkpoint ensures that all of the ____ have been duplicated without damage
Upon failure it either attempts to complete ___ or ___ it
Mitotic phase
Chromosomes
DNA replication
Repair
M checkpoint:
Occurs near the ___ stage of ____
It is also known as the ____ because it determines whether the ___ are attached correctly to the ____
Metaphase stage of Karyokinesis
Spindle Attachment Checkpoint
Sister Chromatids
Spindle microtubules
In addition to the checkpoints, there are ___ that regulate the cell cycle.
They either promote progress of the cell into the next phase called ____
Or they halt the cycle called ____
Regulatory molecules
Positive regulation
Negative regulation
Regulatory molecules:
The failure of a single regulator may have almost no effect on the cell cycle, especially if more than one mechanism controls an event
However, the effect of a deficient or ____ can be wide-ranging ang possibly fatal if multiple processes are involved
Non-functioning regulator
Positive regulation:
There are two types of proteins which are responsible for the progress of the cell through various checkpoints
However, the ___ only regulate when bound to the ___
A ____ is an enzyme that transfers a phosphate group onto a protein through phosphorylation
Cyclins
Cyclin-Dependent Kinases (Cdks)
Kinase
Initiation of Mitosis:
____ The protein complex which initiates the mitotic phase of the cell cycle
It is made up of :
____ Oscillates in quality during the cell cycle. High concentrations necessary to enter M phase, low concentration necessary to leave M phase
_____ Constant quantity and encoded by the ___ gene. Only functional when bound to its cyclin.
Mitosis-promoting Factor
Cyclin B
CDC2 Kinase
CDC2
Initiation of Mitosis:
Once mitosis has been initiated, the ___ decrades the Cyclin B protein of the Mitosis Promotion Factor
It also causes the separation of ___ at the start of ___
Anaphase-Promoting Complex (APC)
Sister Chromatids
Anaphase
Negative regulation:
Best understood ____ are (3):
___ a group of tumor-suppresor proteins common in many cells
The number designations refer to the functional molecular masses of the proteins known as _____
Negative Regulatory Molecules
Rb
p53
p21
retinoblastoma protein
Kilodaltons
Negative regulation:
A faulty copy of a regulatory protein may cause cells to replicate uncontrollably becoming ____
Rb, p53, p21 primarily act at the ____
cancerous
G1 checkpoint
Cancer cells can become tumors
___ remain clustered and can be removed
____ are able to ___ or break away and form new tumors
____ are substances that promote cancer
Benign tumors
Malignant tumors
Metastasize
Carcinogens
Negative regulation:
____ acts when there is damaged DNA in cells undergoing preparatory processes in G1
It halts the cell cycle and recruits ___ to repair the DNA and if it cannot be repaired, it triggers ___ to prevent the duplication of damaged chromosomes
p53
Enzymes
Apoptosis
Negative regulation:
As ___ levels rise, the production of ___ is triggered which enforces the halt of the cell cycle by binding and inhibiting the activity of ____
As a cell is exposed to more stress, higher levels of these proteins accumulate making it less likely that a cell will move into ____
p53
p21
cdk/cyclin complexes
S phase
Negative regulation:
____ exerts its regulatory influence on other positive regulator proteins.
It usually monitors cell size.
It binds to proteins called ____, namely the one called ____ which “turn on” specific genes to produce certain proteins.
Rb Retinoblastoma Tumour Suppressor Protein
Transcription Factors
E2F
Negative regulation:
As the cell increases size, the RB is phosphorylated by ____ / ____ In turn, RB releases E2F which activates the ____ also known as ____
Cyclin D + CDK4
Cyclin D + CDK 6
Transition Protein
Cyclin E
Apoptosis is also known as ____
It occurs in normal development when cells are temporarily required for a maturation process. It also occurs in genetically damaged cells.
An example being (2)
Programmed Cell Death
Embryonic Development
Metamorphosis
Apoptosis:
A well-known example of apoptosis is in the animal ____
It is signaled by the ____ which causes the animal to digest their tail cells, reabsorbing and recycling the digestion products into new structures
Frog
Thyroid hormone
Cells that die from an unexpected injury undergo ____ which is an accidental death.
Necrosis
Key differences between apoptosis and necrosis:
In nectrotic cells, the ____ does not shrink or fragment
In necrotic cells, ____ form but fuse
In necrotic cells, the ____ bursts to release the cell contents into the extracellular environment
Nucleus
Blebs
Cell membrane
Key differences between apoptosis and necrosis:
Nucleus in this case does ____
In cells undergoing apoptosis, the blebs turn into ____ and the cell contents are not released into the extracellular environment
fragment
Apoptotic bodies
