Cell Cycle - Interphase

What are the three phases in the cell cycle

• Interphase

• Mitosis

• Cytokinesis

What are the three phases in Interphase

• G1 Phase

• S phase

• G2 Phase

What happens in G1 phase

Organelles are duplicated

• mitochondria + chloroplasts -self replicate through binary fission

• to allow each daughter cell to have the same number of organelle

DNA - uncondenses - so RNA polymerase can access genes

Cell grows - gains more cytoplasm

New proteins are made

Many active processes are taking place = requiring high rate of respiration

What happens in the S phase

DNA REPLICATION

as cannot start mitosis safely without replication

What happens in G2 phase

• Cell further grows

• further photosynthesis and respiration needed for energy

What are the three checkpoints in the cell cycle

• G1/S checkpoint

• G2 checkpoint

• metaphase checkpoint

What happens in the G1 checkpoint

• restriction point

• cells can only pass if they have grown large enough

• if organelles have been duplicated successfully

• has chemicals needed for replication

• no DNA damage

• no large scale chromosomal mutations (chromosomes split in half/damaged by UV radiation)

What happens in G2 checkpoint

• checks that DNA has been fully replicated without any errors

• makes sure that any DNA damage has been repaired

• checks if cell is large enough + has enough energy supply for mitosis

What happens if it does not pass any checkpoint

• self destruct (apoptosis) = prevents potential cancerous cells from dividing

• cells also attempt to repair damage

• IF CANNOT then = enter G0 phase

What is G0 phase

• phase that allows a cell to exit cell cycle

• some in G0 due to damage or due to cell type

• (neurons/rbc) - enter forever