6.1 Cell Cycle

Question 1

What is the cell cycle

Answer 1

a highly ordered sequence of events that takes place in a cell, resulting in division of the cell and formation of 2 identical daughter cells

Question 2

What are the stages of the cell cycle

Answer 2

interphase, G1, S, G2, mitosis, cytokinesis

Question 3

What is interphase in the cell cycle

Answer 3

long periods of normal working and growth between the small sections of dividing. A cell spends most of their time in this phase

A very active phase, where:

1. DNA is replicated and checked for errors in nucleus
2. protein synthesis occurs
3. mitochondria divide and grow
4. normal metabolic processes occur

Question 4

What are the 3 stages of interphase in the cell cycle

Answer 4

G1, G2, S

Question 5

What is G1

Answer 5

first growth phase:

cell increases in size because organelles replicate, proteins from organelles are produced

Question 6

What is S phase

Answer 6

synthesis phase:

DNA is replicated in the nucleus

Question 7

What is G2

Answer 7

second growth phase:

cell continues to increase, energy stores are increased, duplicated DNA is checked for errors.

Question 8

What’s the miotic phase in the cell cycle

Answer 8

the period of cell division; involves 2 stages:
mitosis (nucleus divided)
cytokinesis (cytoplasm divides and 2 cells are produced)

Question 9

What’s G0 in the cell cycle

Answer 9

name given to the phase when the cell leaves the cycle temporarily or permanently

Question 10

why does G0 occur in the cell cycle

Answer 10

1. DIFFERENTIATION - a cell that becomes specialised to carry out a specific function so no longer able to divide; WON’T ENTER CYCLE AGAIN
2. DAMAGED DNA SO NOT VIABLE - damaged cell enters G0 permanently and no longer divides
   (NORMAL CELLS EVENTUALLY BECOME SENESCENT AND CAN ONLY DIVIDE A LIMITED NO. OF TIMES)
3. as we age, the no. of cells in our body increases, growing numbers of senescent cells have been linked to age related diseases like cancers and arthritis.

Question 11

What type of cells can enter the cell cycle again after being in G0

Answer 11

lymphocytes are an example, in an immune response, can go back out an divide to protect the body from pathogens

Question 12

How can the fidelity of the cell cycle be controlled

Answer 12

by having checkpoints in the cell cycle

Question 13

What do checkpoints monitor in the cell cycle

Answer 13

1. DNA has been replicated correctly, or repaired correctly
2. a cell has grown to its biggest before division happens
3. chromosomes are in the right place before mitosis

Question 14

What do checkpoints specifically do in the cell cycle

Answer 14

they’re the control mechanisms of the cell;
verify whether the stage of the cycle that’s just happened has been completed correctly before the cell goes into the next cycle

Question 15

what are the checkpoints in the cell cycle

Answer 15

G1 checkpoint, G2 checkpoint, spindle assembly checkpoint (metaphase checkpoint)

Question 16

what happens as each checkpoint

Answer 16

G1 checks for: cell size, nutrients, DNA damage (happens at end of G1, before S phase - triggers DNA replication if ready)
G2 checks for: cell size, DNA replication, DNA damage (end of G2, before miotic phase - if ready, cell starts mitosis)
spindle point checks for: chromosome attachment to spindle (happens during metaphase of mitosis when chromosomes have aligned and attached to spindles correctly)