cell cycle

Question 1

list the stages of the cell cycle in order

Answer 1

• interphase
• mitotic phase (PMAT)

Question 2

outline what the happens at each stage of the cell cycle

Answer 2

• interphase: period of normal functioning, growth and DNA replication in preparation for mitotic phase
• mitotic phase: mitosis and cytokinesis - period of cell division

Question 3

list 3 stages of interphase

Answer 3

• G1
• S
• G2

Question 4

describe what happens at each stage of interphase

Answer 4

• G1: proteins from which organelles are synthesised are produced, organelles replicate and cell increases size
• S: DNA is replicated
• G2: cell increases size, energy stores increase, duplicated DNA checked for errors

Question 5

list 2 stages of mitotic phase and outline what happens at each stage

Answer 5

• mitosis: nucleus divides
• cytokinesis: cytoplasm divides and two cells are produced

Question 6

describe the significance of G0 as a phase that cells enter when they leave the cell cycle.

Answer 6

• differentiatiion - specialised cells no longer divide - they carry out their function indefinitely + do not enter cell cycle again
• damaged DNA - damaged cells can no longer divide, preventing cancer
• regulates number of cells in tissues

Question 7

define G0

Answer 7

phase when cell leaves the cell cycle temporarily or permanently

Question 8

outline the role of checkpoints that control the cell cycle

Answer 8

• ensures a cell only divides once grown to right size
• ensures replicated DNA is error free
• ensures chromosomes are in correct positions during mitosis

Question 9

give 3 examples of cell cycle checkpoints

Answer 9

• G1 checkpoint
• G2 checkpoint
• M checkpoint (spindle assembly checkpoint)

Question 10

state where G1 checkpoint occurs

Answer 10

at the end of G1 phase, before entry into S phase

Question 11

describe what is checked at G1 checkpoint

Answer 11

cell size, nutrients, growth factors, DNA damage

Question 12

describe what happens if a cell passes/fails G1 checkpoint

Answer 12

• requirements satisfied = DNA replication begins
• requirements not satisfied = cell enters G0

Question 13

state where G2 checkpoint occurs

Answer 13

at the end of G2 before start of mitotic phase

Question 14

describe what is the checked at G2 checkpoint

Answer 14

cell size, DNA replication, DNA damage

Question 15

describe what happens if a cell passes/fails G2 checkpoint

Answer 15

• requirements satisfied = molecular processes that signal beginning of mitosis initiated
• requirements not satisfied = cell pauses at G2 to try + repair, if irreparable cell undergoes apoptosis

Question 16

state where M checkpoint occurs

Answer 16

during metaphase of mitosis

Question 17

describe what is checked at the M checkpoint

Answer 17

if all chromatids are correctly attached to spindle fibres

Question 18

describe what happens if a cell passes/fails M checkpoint

Answer 18

• requirements satisfied = cell continues mitosis
• requirements not satisfied = mitosis paused, repair attempted