The Eukaryotic Cell Division Cycle - Lecture One Flashcards
What is the cell cycle
An ordered sequence of events that ensures duplication of the entire genome and equal partitioning of the two copies into genetically identical daughter cells
What are the main phases of the cell cycle
G1, S, G2, M
What occurs during the gap phases
They allow time for cell growth but they also provide time for the cell to monitor the internal and external environments to ensure the conditions are suitable and preparations for S/M phase are complete
What occurs during S phase
DNA replication and replication of the chromatin proteins
What triggers chromosome duplication
The activation of S-Cdk
What does the activation of S-Cdk cause
It activates proteins that unwind the DNA and initiate its replication
Once a replication origin is activated what does S-Cdk inhibit
Proteins that are required to allow that origin to initiate DNA replication again
What are the stages of mitosis
Prophase, prometaphase, metaphase, anaphase, telophase
What happens during prophase
Within the nucleus the replicated chromosomes condense. Outside the nucleus, the mitotic spindle assembles between the two centrosomes
What happens in prometaphase
The breakdown of the nuclear envelope
What does the breakdown of the nuclear envelope allow
The chromosomes to attach to the mitotic spindle
What happens during metaphase
The chromosomes are aligned at the equator of the spindle. The kinetochroe microtubules attach sister chromatids to opposite poles of the cell
What happens in anaphase
The sister chromatids synchronously separate to form two daughter chromosomes and each is pulled slowly towards the spindle pole it faces
What happens to the microtubles that has to pull the sister chromatids towards the opposite poles
They get shorter
What two processes contribute to chromosome segregation
The kinetochore microtubules shortening and the spindle poles moving apart
What happens during telophase
The two sets of daughter chromosomes arrive at the poles of the spindle and decondense. A new nuclear envelope reassembles
What occurs after telophase
Cytokinesis
What begins cytokinesis
The contraction of the contractile ring
What happens in cytokineses
The cleavage of the cytolasm
What is the contractile ring composed of
Actin and myosin filaments
What is the cell-cycle control system
A connected series of biochemical switches
What are the cell-cycle control points in an eukaryotic cell
The start (restriction) point, G2/M checkpoint and the metaphase-anaphase checkpoint
At which checkpoint does the cell commit to cell-cycle entry
The start point
What checkpoint triggers early mitotic events
G2/M checkpoint
Which checkpoint stimulates sister-chromatid separattion
Metaphase-anaphase chekpoint
The expression of what can also control the cell
Cyclins and Cdks
What is the function of APC/C
It catalyses the ubiquitylation of regulatory proteins involved in primarily in the exit from mitosis
What specific cyclins does APC/C target
Securin, S-cyclins and M-cyclins
What is the function of SCF
It catalyses the ubiquitylation of regulatory proteins involved in G1 control
What is the function of CAK
It phosphorylates the activation sites in Cdks
Function of Wee 1 kinase
It phosphorylates inhibitory sites in Cdks
What does Wee 1 kinase primarily inhibit and when
Cdk1 activity before mitosis
Function of Cdc25 phosphate
It removes inhibitory phosphates from Cdks
What does Cdc25 phosphate control
The activation of Cdk1
What catalyses the ubiquitylation of SCF
Phosphorylation of p27 by Cdk2
What does Sic1 suppress
Cdk1 activity in G1
What causes the destruction of Sic1
The phosphorylation of Cdk1 at the end of G1
Function of p27
It suppresses G1/S-Cdk and S-Cdk activities in G1
Function of p21
It suppresses G1/S-Cdk and S-Cdk activities after DNA damage
Main mutations of cancer cells
Divide quickly, escape internal and external controls on division and avoid apoptosis
One of the most important tumor suppressor proteins
p53
Where does p53 normally act
At the G1 checkpoint where it blocks cell cycle entry in response to DNA damage and other unfavorable conditions
