Cell Replication

Question 1

Factors that effect rate of cell division

Answer 1

Embryonic vs adult
System complexity
Necessity for renewal
Age
State of differentiation
Tumours

Question 2

Why must cell division be regulated

Answer 2

Premature/abnormal mitosis = cell death
Abnormal no: chromosomes = tumours (aneuploid)
Mutations in oncogenes/tumour suppressor genes = tumors

Question 3

What is the cell cycle

Answer 3

Orderly sequence is events of involving cell duplication, division + coordination

Question 4

Why mitosis most vulnerable stage

Answer 4

Dna damage can’t be repaired
Cells more easily killed
Gene transcription silenced
Cell metabolism is low

Question 5

Function is centrosome

Answer 5

Microtubules organising centre + formation is mitotic spindle

Question 6

Cell cycle stages

Answer 6

G0 = quiescent
G1 = gap 1
S = dna replication
G2 = gap 2
M = mitosis + cytokinesis

Question 7

Prophase

Answer 7

Chromatin condensation
Nucleolus disintegration
Mitotic shingle fibre formation in centrosomes

Question 8

Metaphase

Answer 8

Chromosomes aligned in centre
Nuclear membrane breakdown
Spindle formation complete
Attachment of spindle to chromosomes via kinetochore

Question 9

Anaphase

Answer 9

Cohesin breakdown (holds sister chromatids together)
Microtubles contract - pull chromosomes pulled apart towards poles
Organelles divide equally
Centrosomes migrate apart

Question 10

Telophase

Answer 10

Daughter chromosomes at poles
Nuclear envelope reassembles at both poles

Question 11

Cytokinesis

Answer 11

Cytoplasm splits into 2 daughter cells

Question 12

G2

Answer 12

Rapid cell growth and protein synthesis while cell preps for mitosis
Varies in diff cell types

Question 13

G0

Answer 13

Quiescent phase
Cell cycle machinery dismantled

Question 14

G1

Answer 14

Synthesis of mRNA + proteins in preparation for S phase + M

Question 15

S

Answer 15

Dna replication (nuclear + mitochondrial)
Protein synthesis
Replication of organelles

Question 16

What is the first cell cycle checkpoint

Answer 16

G1 - before entering S
Is environment favourable?
(nutrients and growth factors available)

Question 17

Second cell cycle checkpoint

Answer 17

G2 - entering M
Is all dna replicated?
Is all dna damage repaired?

Question 18

Third checkpoint in cell cycle

Answer 18

During Mitosis - entering anaphase
Are all chromosomes attached to spindle correctly

Question 19

How do cells leave G0

Answer 19

Growth factor binds growth factor receptor on cell surface
Triggers intracellular signalling pathway
Phosphorylation by kinase intermediates
Increase in protein synthesis/inhibition of degradation = cell growth

Question 20

What is C-Myc

Answer 20

Oncogene/Transcription factor
Expression induced by growth factor signalling pathways

Question 21

Function of C-Myc

Answer 21

Stimulates expression of cell cycle genes
Promoted G0 to G1 transition

Question 22

Cdk function (basic)

Answer 22

Phosphorylation or de phosphorylation of molecules
Allows control of events in cell cycle

Present in all proliferating cells but only active when cyclin bound

Question 23

What activates cyclin

Answer 23

C-Myc