Chapter 17 Flashcards
What are the different phases in the cell cycle
Interphase :
G1 phase
S phase
G2 phase
M phase
Mitosis
CytokinesisWhat happens in the prophase ?
Condensation of chromosomes;
Centrosomes have duplicated and the mitotic spindles form
What are condensins
5- subunit protein complex that reassembles cohesion
What happens in prometaphase
Nuclear envelop breaks down; spindles connect to chromosomes by their kinetochores and begin movement
What triggers the formation of the mitotic spindle
M-Cdk
What happens in meta phase
Chromosomes align at equator of each spindle pole by way of the microtubules of the mitotic spindle
What happens in anaphase
The sister chromatids separate to form daughter chromosomes that are pulled apart towards the spindle pole microtubules shorten and pokes move more apart
What happens in telophase
The daughter chromosomes decondense ; nuclear envelope reassembles ; contractile ring begins to contract
What happens in cytokinesis
Nuclear envelop surrounds chromosomes
Contractile ring has created cleavage furrow and cytoplasm is divided in two
This acts as a microtubule organizing center
Centrosomes
When does the duplication of the centrosomes begin and complete
S-phase
G2
Which protein help keeps the poles apart
Kinesin-5
Which proteins pulls poles toward each other
Kinesin-14
These proteins pushed chromosomes away from poles
Kinesin-4
These proteins keep spindle poles away from each other and near cortex
Dyneins
What is the arrangement of the sister kinetochores
Back - back
What protein helps remove cohesions in anaphase
Separase
What activated separase
Anaphase promoting complex
APC/C
What is an active anaphase promoting complex reffered as
Ubiquitin ligase
Degraded proteins like M-Cdk
What keeps separase inactive
Securin
How does the separase become active to remove cohesions
When APC/C becomes active it adds ubiquitin to securin which targets it for degradation which will allow separase to become active and will then degrade the cohesion of the sister chromatids
What happens in anaphase A
Sister chromatids separate
What happens in anaphase B
Spindle pokes move away from each other
What is the contractile ring made of
Actin and myosin Filaments
What allows the formation of parallel actin bundles in the contractile ring
Formin
What needs to be activated in order for the contractile ring to assemble and contract
RhoA
Name the phases of the cell cycle
G1
S phase
G2 phase
M phase
What gives the cell cycle its quality control feature
Various checkpoints
G1/S -
G2/M
Metaphase ti anaphase
What mediates the transition from one phase to another in the cell cycle
By cyclins and
Cyclin dependent kinases ( Cdk)
When is Cdk active
When bound to cyclin
Will progression of phases continue if Cdk is active
No
The expression of this changes with the stages of the cell cycle
Cyclin
How is the Cdk activated by cyclins
When cyclin is not present Cdks active site is blocked by a loop
When cyclin is bound to Cdk the loop is removed and activated Cdk
When Cdk is active in the G1/S - G2/M phase what does it do to various proteins
Phosphorylates them so that the cell cycle progresses
In comparison with the progression of the G1/S -G2/M stage what is the different in the metaphase to anaphase progression
Metaphase to ananphase progression requires degradation not phosphorylation
What promotes the replication of DNA only once during the cell cycle
S-Cdk
How are the sister chromatids held together after the DNA has been replicated
Cohesions
What is the name of the stage in the cell cycle where cell divides in 2 daughter cells
Mitosis
What mediates crossing over
Synaptomenal complex
What happens in meiosis I
Homologous chromosomes pair together
Non sister chromatids exchange genetic material ( crossing over )
What is one difference from meiosis I and meiosis II
In meiosis I it is the separation of the homologous chromosomes
In meiosis II it’s separation of sister chromatids
Nondisjunctuon
Phenomenon that when homologs fail to separate properly
Some haploid gametes have more copies of chromosomes while others lack chromosome
What are extracellular factors that influence cell growth and division
Mitogens
Growth factors
Survival factors
What do mitogens do
Promote cell division
They activate Ras and MAP kinase pathway
Triggers G1- Cdk and S -Cdk to activate
In what phase does chromosome duplication occur
S Phase
(DNA ) synthesis
In what phase of the cell cycle does chromosome segregation and cell division occur
M-Phase
What is the mitotic spindle
Giant bipolar array of microtubules
G1, S, G2 are together called
Interphase
Which phase requires the most time
Interphase
Why are the gap phases G1 and G2 important
Provides time for the cell to monitor the internal and external environment to ensure conditions are suitable to proceed to S phase and mitosis
What what are two components of the cell cycle control system
Cyclin
Cyclin dependent protein kinase ( Cdk)
What helps the cyclin Cdk complex become fully activated
CAK
Cdk- activating kinase
It phosphorylates an amino acid near the entrance of the Cdk active site
What is the key regulator of the metaphase to anaphase transition
APC/ C
(Anaphase promoting complex
Cyclosome)
What are the two proteins that APC/C target for destruction
Securins - hold sister chromatids together
S- and M- cyclin s - inactivated most Cdks in the cell
How does cyclin activate Cdk
It binds causing a loop to move away from the active site
What type of enzyme is APC/C
Ubiquitin ligase
What inactivates cyclin Cdk complexes in
CkIs ( Cdk inhibitor proteins
