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The sequential events of the cell cycle are directed by a distinct cell cycle control system, which is similar to a clock The cell cycle control system is regulated by both internal and external controls The clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received
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Figure 5.18d
Hydrogenbond
Disulfidebridge
Polypeptidebackbone
Ionic bond
Hydrophobicinteractions andVan der Waalsinteractions
PROTEIN STRUCTURE DISRUPTED DENATURED PROTEIN
• The sequential events of the cell cycle are directed by a distinct cell cycle control system, which is similar to a clock
• The cell cycle control system is regulated by both internal and external controls
• The clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received
Stop and Go Signs: Internal and External Signals at the Checkpoints
• Three important checkpoints are those in G1, G2, and M phases
Figure 12.17a
G1 checkpoint
G0
G1
Without go-ahead signal,cell enters G0.
(a) G1 checkpoint
G1
With go-ahead signal,cell continues cell cycle.
Figure 12.17b
G1
M G2
G1
M G2
M checkpoint
Without full chromosomeattachment, stop signal isreceived.
PrometaphaseAnaphase
G2 checkpointMetaphase
With full chromosomeattachment, go-ahead signalis received.
(b) M checkpoint
• It is critical that checkpoint proteins function properly. (they need the correct structure!)
• Broken Stop sign TUMOR• Mutated Stop sign TUMOR• There are DNA REPAIR ENZYMES to fix
mutated genes prevent malformed proteins. (link), (and this time, to music…)
• BRCA1 and BRCA2 = tumor suppressor genes• Code for DNA repair enzymes• They fix mutations prevent the
production of misshaped proteins.
• What happens if BRCA1 or BRCA2 mutated?• Some mutations may go un-repaired.
• Increased RISK of a tumor:
Mutated Stop Sign TUMORMutated Stop Sign, Repaired NO TUMORMutated Stop Sign, REPAIR ENZYME BROKEN TUMOR
LINK TO ANJELINA JOLIE DOUBLE MASTECTOMY, REMOVAL OF OVARIES AND FALLOPIAN TUBES- CNN
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