Cell cycle

What are the two main parts of the cell cycle?

Mitotic phase and interphase

What stages is interphase divided into?

• G1 phase

• Synthesis phase

• G2 phase

What happens during G1?

• Organelles replicate- requires lots of protein so transcription and translation take place

• Transcription/translation

• Size of call increases - Ensure daughter cells are the correct size

What happens during synthesis phase?

• DNA synthesis

• Chromosomes replicated

What happens during G2 phase?

• Energy stores are replaced

• Transcription and translation

• Chromosome repair - If chromosomes have been damaged

• Size of selling increases

What two parts can mitosis be divided into?

• Mitosis – chromosome separate into two nuclei

• Cytokinesis – cell divides into two

What is the G0 Phase?

When cells exit the cell cycle

Why do cells enter the G0 phase?

• Fully differentiated cells enter and stay there for the rest of their lives E.g. neurons

• Senescent cells – damaged DNA

• Some cells into G0 temporarily e.g. B memory cells – cells can be triggered to re-enter cell cycle during an infection

What happens if a cell fails a checkpoint?

It will leave the cell cycle and enter G0

What is the first checkpoint and where is it located in the cell cycle and what is checked?

• Before S phase cell must pass through G1 checkpoint – cell checks that it has grown to the correct size, and checks for DNA damage. If the cell satisfies the G1 checkpoint the it passes onto S phase and carries out DNA replication

What is the 2nd checkpoint

G2 checkpoint, cell checks for DNA damage and that it has grown to correct size.

What is the 3rd checkpoint

Metaphase checkpoint, checks chromosomes are assembles correctly on the mitotic spindle