Cell cycle

Question 1

Phase of the cell cycle and checkpoints: M phase

Answer 1

• checkpoint triggers condensation of chromatin

- halfway through the cell cycle the metaphase checkpoints ensure that the cell is ready to complete mitosis

Question 2

Events that happen within the cell: M phase

Answer 2

• cell growth stops
• nuclear division
• cytokinesis

Question 3

Phase of the cell cycle and checkpoints: Gap Phase 0

Answer 3

• resting phase triggered during early G1 at the restriction checkpoint by a checkpoint chemical
• some cells such as epithelial cells do not have this phase

Question 4

Events that happen within the cell: Gap phase 0

Answer 4

• may undergo go apoptosis, differentiation or senescence

- some types of cells such as neurones remain in this phase for a long time or indefinitely

Question 5

Phase of the cell cycle and checkpoints: Gap Phase 1

Answer 5

• a G1 checkpoint control mechanism ensures that the cell is ready to enter the S phase and begin DNA synthesis

Question 6

Events that happen within the cell: Gap Phase 1

Answer 6

• cells grow and increase in size
• transcription of genes to make RNA occurs
• Organelles duplicate
• Biosynthesis, e.g. protein synthesis and making the enzymes needed for DNA replication in the S phase
• p53, the tumour suppressor gene helps control this phase

Question 7

Phase of the cell cycle and checkpoints: S phase

Answer 7

• the chromosomes are unwound and the DNA is diffuse
• every molecule of DNA is replicated, specific sequence to the replication of genes
• genes that are active in all types of cells are duplicated first
• genes that are normally inactive in specific types of cells are replicated last

Question 8

Events that happen within the cell: S phase

Answer 8

• once the cell has entered this phase it is committed to completing the cell cycle
• DNA replicated
• when all chromosomes have been duplicated each one consists of a pair of identical chromatids
• rapid as the exposed DNA pairs are more susceptible to mutagenic agents this reduces the chances of spontaneous mutations happening

Question 9

Phase of the cell cycle and checkpoints: Gap Phase 2

Answer 9

special chemicals ensure that the cell is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and in formation of the spindle

Question 10

Events that happen within the cell: Gap phase 2

Answer 10

• cells grow