Cell Cycle Flashcards
1
Q
G1 and G2
A
G1
- growing in size
- monitoring environment
- RNA and protein synthesis in preparation for S phase
- growth factor dependent
G2
- further growth
- cell organelle replication
- preparation for mitosis
2
Q
Prophase
A
- chromatin condensation
- nucleolus disappears
- centrioles move to poles
3
Q
Pro-metaphase
A
- nuclear membrane dissolved
- chromosomes attach to microtubules and begin moving
4
Q
Metaphase
A
- spindle fibres align the chromosomes along the middle of the cell nucleus/metaphase plate
5
Q
Anaphase
A
- paired chromosomes separate and move to opposite sides of the cell
6
Q
Telophase
A
- chromatids arrive at opposite poles of cell
- new membranes form around daughter nuclei
- chromosomes decondense
- spindle fibres disperse
7
Q
CDK’s
A
- regulate progression through the cell cycle
- serine/threonine kinases
- activity must be tightly regulated: cyclins, phosphorylation/ dephosphorylation, CKI’s
- CDK4+6: g1
-CDK 2: s - CDK 2: g2-m
- CDK 1: g2-a
8
Q
Cyclins
A
- activator proteins that are up- or down regulated depending on the phase of the cell cycle
- unstable proteins
- did dents cyclins associated with different CDK’s
- CDK 4/6: cyclin D
- CDK 3: cyclin E
- CDK 2: cyclin A
- CDK 1: cyclin B (maturation promoting factor)
9
Q
CDK inhibitors
CKI’s
A
- small proteins that block cyclin/CDK activity
- worthier by forming an a inactive complex or by acting as a competitive CDK ligand
Three families: p21 CIP, p27 KIP, p16 INK
10
Q
Progression from G2 to M phase
A
- progression to M phase is dependent on cdk1/ cycling B
- cyclin B levels start to rise in G2 in preparation
11
Q
MPF activation
A
-nuclear envelope destroyed: lamins
- chromosomes condensation: condesnins histones
- spindle formation: microtubule- associated proteins (MAPs)
12
Q
Checkpoints monitor:
A
- favourable external environment (presence of growth factors)
- favourable internal environments (sufficient growth)
- DNA damage, replication errors, spindle attachment, chromosome integrity
13
Q
Restriction point
A
- cell cycle progression is determined by the presence of growth factors
sufficient signal-> cell cycle progression-> insufficient signal-> cell cycle arrest - The points in G1 after which the cell no longer requires growth factors to complete the cell cycle and commits to cell division
-dependent on the accumulation of cyclin D - 2-3 hours prior to initiation of S phase
- RB protein acts as a gatekeeper at the restriction point
14
Q
Restriction point
A
- cell cycle progression is determined by the presence of growth factors
sufficient signal-> cell cycle progression-> insufficient signal-> cell cycle arrest - The points in G1 after which the cell no longer requires growth factors to complete the cell cycle and commits to cell division
-dependent on the accumulation of cyclin D - 2-3 hours prior to initiation of S phase
- RB protein acts as a gatekeeper at the restriction point
15
Q
RB: tumour suppressor
A
- TSG’s encode normal cell proteins that inhibit cell proliferation and growth of cell maintain the integrity of the genome
- cause fell fuel arrest in abnormally dividing cells and repair DNA damage aka the brakes of the fell
RB: blocks entry to cell cycle
P53: detects DNA damage
BRCA1: DNA repair
16
Q
DNA damage checkpoint
A
- DNA damage-> p53-> p21-> p21-> CDK or Cyclin or cell cycle inhibition
CDK: late G1 (G1/S) cdk2- cyclin E/A
Cyclin: late G2 (G2/M) (CDK1- cyclin A/B)
17
Q
p53
A
- a transcription fafir
- inhibits cell cycle progression (low levels results in p1 expression)
- allows DNA repair
- promotes apoptosis
- cellular stress (dna damage) causes cellular responses ( cell cycle arrest, dna repair, apoptosis)
18
Q
Spindle assembly checkpoint
A
- surveillance mechanisms delay anaphase
• unattached chromosomes, checkpoint is on and anaphase is inhibited
• chromosomes attached, inhibition of anaphase is alleviated - anaphase promoting complex (APC) is inhibited until all chronicles are attached
