Check Points

Question 1

Define check points

Answer 1

Critical control point at which the cell monitors its internal equilibrium where stop and go-ahead signals can regulate cell cycle

Question 2

Where are the 3 check points?

Answer 2

1. G1-S
2. G2-M
3. M

Question 3

What do the check points do?

Answer 3

1. Detecting the presence if unreplicated or damaged DNA

2. Ensure chromosomes are intact and that critical stages of the cell cycles are completed.

Question 4

What happen at G1-S check point?

Answer 4

• assessment of cell growth*
• cell environment assessed for presence of growth factors required to stimulate cell division
• cells are healthy and grown to suitable size
• > protein initiate DNA replication

Question 5

What happen at G2 check point?

Answer 5

• assessment of DNA replication*
• DNA repair enzymes check the results of DNA replication
• > successful: proteins signal the cell to begin the molecular processes that cause cell to divide via mitotic cell division

Question 6

What happen at M check point?

Answer 6

• Monitor: formation of spindle fibres apparatus and attachment of spindle fibres to the kinetochores
• anaphase only begin when all chromosomes are properly attached to spindle at the metaphase plate
• as kinetochores of all chromosomes are properly attached, regulatory protein complex become activated
• > activate separase that cleaves cohesins, allowing sister chromatids to separate

-disruption of cell cycle at checkpoints will lead to unrestrained proliferation of cancer cells
=> genomic instability