[3.8] the cell cycle

Question 1

what are the 3 stages of the cell cycle?

Answer 1

1. nuclear division
2. cytokinesis
3. interphase

Question 2

what happens during nuclear division?

Answer 2

when the nucleus divides either into 2 (mitosis) or 4 (meiosis)

Question 3

what happens during cytokinesis?

Answer 3

division of the cytoplasm to produce 2 (mitosis) or 4 (meiosis) new cells

Question 4

what are 3 examples of things that can happen in interphase?

Answer 4

• DNA replication by semi-conservative replication
• organelle replication
• protein synthesis

Question 5

what are the 3 substages of interphase?

Answer 5

G1) ‘gap’ phases, also used as checkpoints for eg. errors in DNA synthesis
S) synthesis stage
G2) ‘gap’ phases
- interphase is sometimes known as the resting phase because no division takes place

Question 6

what are stem cells

Answer 6

cells that retain the capacity to undergo the cell cycle, therefore producing more cells
> most cells cannot do this

Question 7

what is the importance of stem cells being able to produce more cells?

Answer 7

• growth of an organism
• repair of damaged tissues
• replacement of damaged cells
• asexual reproduction in unicellular organisms

Question 8

what is cancer?

Answer 8

a condition resulting from mutations in the genes that control the rate of the cell cycle

Question 9

what are the 2 groups of genes that control the rate of the cell cycle?

Answer 9

• proto-oncogenes: these normally increase the rate of the cell cycle
• tumour suppressor genes: these normally decrease the rate of the cell cycle

Question 10

what happens when either of the 2 genes that control the rate of the cell cycle mutates?

Answer 10

• the balance between them is lost
• this results in the cell cycle happening faster than normal
• this leads to a rapid, uncontrolled growth of cells that haven’t formed properly ie. a cancerous tumour

Question 11

how are tumours usually treated?

Answer 11

• surgery
• radiotherapy
• chemotherapy (ie. drug treatment)

Question 12

what two aspects of the cell cycle do chemotherapy drugs usually target?

Answer 12

• preventing DNA replication in interphase
• preventing formation (prophase/metaphase), attachment (metaphase), and action (anaphase) of spindle fibres

Question 13

what is the effect of the drugs on healthy cells?

Answer 13

• these drugs will therefore also affect healthy cells, especially if they are naturally rapidly dividing cells eg. skin, hair
• the aim is for the drugs to damage the tumour cells to a greater extent than healthy cells