Cell Replication Flashcards
What is the s phase of the cell cycle?
DNA Replication.
What is the M phase of the cell cycle?
Mitosis and cytokinesis.
What is G₀ ?
The G₀ phase describes a cellular state outside of the replicative cell cycle. Carrying out cell functions.
What transcription factor promotes G0 to G1 transition?
c-Myc
In tumours what is wrong with c-Myc?
Overexpressed.
What leads to expression of c-Myc
Growth factor signalling pathway.
When is cyclin concentration highest?
During mitosis.
When is cyclin concentration increasing?
During interphase.
When are cdk (cyclin dependent kinase) most active?
During mitosis.
What does c-Myc do?
Promotes production of cyclin D which then activates cdk 4/6 complex. This allows transition from G0 to S phase.
What are the g phases?
Growth phase.
What might halt a cell in G1?
Unfavourable extracellular environment. Damaged DNA.
What might halt a cell in S or G2 phase?
Incompletely replicated DNA.
What might halt a cell in the M phase?
Chromosome improperly attached to mitotic spindle.
What is required for entry to cell cycle?
Cyclin D : Cdk4/6 complex.
Cyclin dependent kinase is regulated by?
Cyclins, phosphorylation and phosphate removal.
What are kinases important for?
Signal amplification and regulation.
How is a cdk activated?
Binding of cyclin and removal of inhibitory phosphate by phosphatase enzyme.
How are cyclins turned off?
Ubiquitination (protein degradation).
What does degradation of cyclins do?
Allows cyclical activation.
What is Rb (retinoblastoma protein)?
A molecular brake. Blocks transcription of proteins for DNA synthesis such as DNA polymerase.
How is Rb activated?
It is phosphorylated.
What does p21 do?
Inactivates inactivates Cdk-cyclin complexes so that DNA can be repaired.
What induces production of p21?
p53.
What kind of protein is p53?
Tumour suppressor.
