Cell Cycle Flashcards
What are the 4 phases of the cell cycle?
G1, S, G2, M
Define the cell cycle
An orderly sequence of events that allows a cell to duplicate its contents and divide in two
Name the 4 essential steps to the cell cycle
Duplicate DNA
Segregate DNA
Maintain size by duplicating other organelles/macromolecules
Coordinate cell growth with cell division
What occurs in S phase of the cell cycle?
DNA replication
What occurs in the gap phases of the cell cycle?
Cell growth by doubling protein mass/organelles
Get ready for next phase
Monitor environment
Why would a cell enter transient G0 phase?
Differentiation
Quiescence
Why would a cell enter permanent G0 phase?
Terminal differentiation
Senescence (something wrong)
Name the 5 phases of mitosis
Prophase Prometaphase Metaphase Anaphase Telophase
Outline prophase
Chromosomes condense, sister chromatids held together by cohesin
Centrosomes move to opposite poles
Spindles assemble
Kinetochore recognition, binding to centromere
Nuclear envelope breaks down
Outline prometaphase
Nuclear envelope disintegration
Chromosomes attach to kinetochores (microtubules)
Tension exerted on chromatids
Outline metaphase
Chromosomes align on spindle equator
Kinetochore microtubules attach chromatids to opposite poles of spindle
Outline anaphase
Sister chromatids separate
Chromatids move to opposite poles
Poles move further apart
Outline telophase
Nuclear envelope reforms
Chromatids de-condense
Cytokinesis initiation
End of mitosis
What is the purpose of the cell cycle control system?
Events in set sequence
Each event is completed before the next starts
Are conditions suitable for division?
What is the cell cycle controlled by?
Cyclin-Cdk complexes
What does Cdk stand for?
Cyclin-dependent kinase
What are the 4 major cyclin families, what Cdk-complexes do they operate with, and where in the cell cycle do they operate?
D - G1 (Cdk4 and 6)
E - S (Cdk2)
A - S (Cdk2) and G2 (Cdk1)
B - M (Cdk1)
What are Cdks?
Serine-threonine protein kinases
Define ‘kinase’
Enzyme that catalyses the transfer of phosphate groups (phosphorylation)
Define ‘phosphatase’
Enzyme that catalyses the removal of phosphate group
G1 cyclin (cyclin D) produced in response to…
External signals
G1/S cyclin (cyclin E) triggers…
Start/entry into cell cycle
S phase cyclin (cyclin A) triggers…
DNA replication
M phase cyclin (cyclin B) triggers…
Spindle assembly and attachment of microtubules to chromosomes
What is CAK?
Cdk-activating kinase
Phosphorylates cyclin-Cdk
What is Wee1?
An inhibitory kinase - phosphorylates cyclin-Cdk (for the second time) hence inactivating it
What is Cdc25?
Activating phosphatase - removes a phosphate group from cyclin-Cdk to activate it (after CAK and Wee1 activity)
