1.5.2 the cell cycle / 1.5.3 control of the cell cycle

Question 1

what does the cell cycle consist of

Answer 1

interphase and mitotic phase

Question 2

what does interphase involve

Answer 2

• growth and DNA synthesis
• G1 - a growth phase
• S phase - DNA replicated here
• G2 - a further growth phase

Question 3

what does mitotic phase involve

Answer 3

mitotis and cytokenesis
- in mitotis the chromosomal material is separated by the spindle microtubules
- this is followed by cytokenesis, in which the cytoplasm is separated into two daughter cells

Question 4

what four phases are there in mitosis

Answer 4

• prophase
• metaphase
• anaphase
• telophase

Question 5

what occurs in prophase

Answer 5

DNA condenses into chromosomes each consisting of two sister chromatids. nuclear membrane breaks down, spindle microtubules extend from the MTOC by polymerisation and attach to chromosomes via their kinetochores in the centromere region

Question 6

what occurs during metaphase

Answer 6

chromosomes are aligned at the metaphase plate (equator of the spindle)

Question 7

what occurs during anaphase

Answer 7

spindle microtubules shorten by depolymerisation, sister chromatids are separated, and the chromosomes are pulled to opposite poles

Question 8

what occurs during telophase

Answer 8

the chromosomes decondense and nuclear membranes are formed around them

Question 9

what is progression through the cell cycle controlled by

Answer 9

checkpoints

Question 10

what do checkpoints control

Answer 10

progression through the cell cycle

Question 11

what are checkpoints

Answer 11

mechanisms within the cell that assess the condition of the cell during the cell cycle and halt progression to the next phase until certain requirements are met

Question 12

what are cyclin proteins that accumulate during cell growth involved in

Answer 12

regulating the cell cycle

Question 13

what do cyclins combine with and activate

Answer 13

cyclin depenent kinases (CDKs)

Question 14

what are CDKs

Answer 14

cyclin dependent kinases

Question 15

what does the combination of cyclin proteins with CDKs form

Answer 15

active cyclin CDK complexes

Question 16

what do the active cyclin CDK complexes phosphorylate

Answer 16

proteins that regulate progression through the cycle

Question 17

when does progression occur

Answer 17

when sufficient phosphorylation is reached

Question 18

what occurs at the G1 checkpoint

Answer 18

• retinoblastoma protein acts as a tumour suppressor
• by inhibiting the transcription of genes that code for proteins needed for DNA replication

Question 19

what does retinoblastoma act as

Answer 19

a tumour suppressor

Question 20

what inhibits the retinoblastoma protein

Answer 20

phosphorylation by g1-cyclin-cdk

Question 21

what does the phosphorylation of retinoblastoma protein allow

Answer 21

the transcription of the genes that code for proteins needed for DNA replication

Question 22

what are the three checkpoints

Answer 22

• G1
• G2
• metaphase

Question 23

what occurs at the g2 checkpoint

Answer 23

the success of dna replication and any damage to dna is assessed

Question 24

what does dna damage trigger

Answer 24

the activation of several proteins including p53 that can stimulate dna repair, arrest the cell cycle or cause cell death

Question 25

what can the activation of proteins such as p53 stimulate

Answer 25

dna repair
arrested cell cycle
cell death

Question 26

what does the metaphase checkpoint control

Answer 26

progression from metaphase to anaphase

Question 27

what occurs at the metaphase checkpoint

Answer 27

progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules

Question 28

what can an uncontrolled reduction in the rate of the cell cycle result in

Answer 28

degenerative diseases

Question 29

what can an uncontrolled increase in the rate of the cell cycle result in

Answer 29

tumour formation

Question 30

what is a proto-oncogene

Answer 30

a normal gene usually involved in the control of cell growth or division, which can mutate to form a tumour promoting oncogene

Question 31

what can a proto-oncogene mutate to form

Answer 31

a tumour promoting oncogene