Cell Proliferation Flashcards
Why is S phase the longest phase of the cell cycle?
Cells replicate DNA but also synthesise chromatin proteins for packaging the copied DNA into chromosomes
What does the cell use G2 phase for?
Delay the commitment of entering mitosis so that the cell can grow, and check if the DNA is faultless
What is formed in G2 phase?
Cyclin B-Cdk1 to allow cells to progress to M phase
How is chromosome segregation prepared in prophase and prometaphase of the M phase?
Cyclin B-Cdk1 phosphorylates proteins which result in condensing of DNA, forming mitotic spindle and breaking down nuclear envelope
What happens if DNA replication is incomplete or if there is unrepaired DNA damage?
Cells cannot pass through G2 phase and enter M phase
What is required for chromosome segregation in metaphase?
Correct attachment of sister chromatids to the spindle
What happens after the chromosomes attach to spindle fibres?
Chromosomes are tugged between the two poles, resulting in them moving to the spindle equator
What happens if incorrect kinetochore attachment occurs?
Requires correction which causes chromosomes to lag in the spindle middle and incur damage later
What happens to unattached kinetochores?
Detected by spindle assembly checkpoint which block entry to anaphase
How are chromatids separated in anaphase: What is the pull by spindles on kinetochores resisted by?
The cohesion of the chromatids
How are chromatids separated in anaphase: How are chromatids connected?
Cohensin proteins
How are chromatids separated in anaphase: What does Cyclin B-Cdk1 do?
Triggers the steps to cause the breakdown of cohensins
How does Cyclin B-Cdk1 deactivation result in the cytoplasm dividing into two?
Deactivation of cyclin B-Cdk1 results in spindle disassembly and reformation of nuclear envelope which enables the cytoplasm to split into two cells
