Cell Cycle

Question 1

Phases

Answer 1

Interphase:
G1 => S => G2 => M
=> G0

Question 2

G1

Answer 2

Gap 1
Growth phase 1
cell growth
organelles copy 
checkpoint 1 part-way along G1
    = growth factors bind to receptors to pass the checkpoint CDK + G1/S - promotes S phase, P53 - checks for gene damage
 - checks for DNA damage
 - checks for nutrients
good => S phase
bad => G0 phase

Question 3

G0

Answer 3

Resting state
No active growth
cell does its job, no replication

Question 4

S

Answer 4

Synthesis phase
DNA replicates
centrosome replicates

Question 5

G2

Answer 5

Gap 2
Growth phase 2
proteins copy
organelles copy
Checkpoint 2 - CDK + M Cyclin protein, encourages prophase
 - at end just before M phase 
 - checks for cell size (density-dependent inhibition 
– crowded cells stop growing)
  - checks for DNA properly replicated

Question 6

M

Answer 6

Mitotic phase
prophase - chromosomes condense, mitotic spindles form, nucleolus dissolves
prometaphase - chromosomes condensed. nuclear envelope breaks down, microtubules grow from mitotic spindles
metaphase - chromosomes line up
anaphase - chromatids are pulled apart by centrioles
telophase - nuclear membrane splits into 2
cytokinesis - cytoplasm splits into 2

Mitosis Checkpoint - APC/C protein
occurs before anaphase
checks all spindles are attached to chromatids

Question 7

Cancer Cells

Answer 7

Don’t need growth factor to divide
avoid regulation, divide unchecked
cancer cells move around body through metastasis
do not undergo programmable cell death (apoptosis)