U1 - Cell cycle Flashcards
What are the two phases in the cell cycle?
Interphase and miotic phase
What does Interphase involve?
Inter phase consists of growth and DNA replication.
What are the three phases of interphase and what happens during them
G1 consists of growth to ready for DNA replication.
S consists of DNA replication
G2 consists of growth phase to ready for Mitosis
What are the two stages in the Miotic phase
Mitosis and Cytokinesis
What is mitosis
Mitosis is the seperation of chromosomal material by the spindle microtubules
What is cytokinesis
Is the seperation of the cytoplasm into two daughter cells.
What are the 4 stages of Mitosis
Prophase, Metaphase, Anaphase and Telaphase (PMAT)
What happens to the DNA during Prophase to prepare it for seperation
The DNA condenses into chromosomes each consisting of two sister chromatids
What happens to the nuclear membrane during Propphase?
The nuclear membrane breaks down.
Where do the microtubules come from and how (during prophase)
The spindle fibres extend from the MTOC by polymerisation
Where do the microtubules attach to
the chromosomes kinetichores in the centronome.
Summarise Prophase
DNA condeses into chromosomes consisting of two sister chromatids
- The nulear membrane breaks down
- Spindle microtubules extend from the MTOC by polymerisation
- They attach to vhromoses via their kinetichores and in the centronome.
Summarise Metaphase
Chromosomes are aligned at the metaphase plate (equator)
Summarise Anaphase
The spindle fibres shorten by depolymeristaion, sister chromatids are seperated and the chromosomes are pulled to opposite poles.
Summarise Telaphase
The chromosomes condense and nuclear membranes are formed around them .
What controls the cell cycle
Checkpoints
What are checkpoints
Mechanisms within a cell that assess the condition of the cell and halt progression to the next phase until certain requiremens are met
What proteins regultate the cell cycle
Cyclin proteins that accumulate during cell growth regulate.
What does Cyclin combine with
Cyclin-dependent kinases (CDK’s)
What does Active CDK’s do?
They phosphorylate proteins that regulate progression through the cycle. If sufficent phosphorylation is reached progression occurs.
What protien is involved in the G1 checkpoint?
Retinablastoma (Rb)
In what stages do checkpoints occur?
End of G1
Start of G2
Metaphase
What happens at the G1 checkpoint
Rb acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication. Phosphorylation by cyclin-CDK inhibits the Rb and progression occurs.
What does retinablastioma do
It acts as a tumour supressor by inhibiting the transcription of genes that code for proteins needed for DNA replication.
What happens at the G2 checkpoint
The success of DNA replication and any damage to DNA is assessed.
What happens if the DNA is damaged at the G2 checkpoint?
The DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death.
What does phosphorylation of Rb by cyclin - CDK allow
It inhibits the Rb so allows the transciption of the gene that code for protein needed for DNA replication. Therefore, can progress from G1 to S.
What happens at the Metaphase checkpoint?
Progression is halted until all chromosomes are aligned correctly on the metaphase plate. Allows progression from Metaphase to Anaphase.
Degenerative disease is caused by…
An uncontrolled reduction in the rate of the cell cycle
Tumour formation is the result of…
An uncontrolled increase in the rate of the cell cycle.
What is a proto-oncogene
Usually involved in the control of cell growh or division, which can mutate to form a tumour- promoting oncogene.
