The Cell Cycle

Question 1

Mitosis

Answer 1

• Type of nuclear division
• Each new daughter cell contains the same genetic information as the parent cell and each other
• Maintains the chromosome number

Question 2

Cytokinesis

Answer 2

Cytoplasmic division following nuclear division, resulting in two new daugther cells

Question 3

The phases of the cell cycle

Answer 3

Mitosis (M) phase –> Gap 0 (G0) phase –> Gap 1 (G1) phase –> Synthesis (S) phase –> Gap 2 (G2) phase

Question 4

Interphase

Answer 4

Umbrella term for all phases surrounding mitosis

Question 5

How long does the cell cycle take for a typical human cell?

Answer 5

24 hours

Question 6

G0 phase

Answer 6

• A ‘stop’ - resting phase triggered during early G1
• Cells may undergo apoptosis, differentiatiom or senescence
• Some cells like neurons remain in this phase for a long time or indefinitely

Question 7

G1 phase

Answer 7

• Gap 1 phase also known as growth phase
• Cells grow and increase in size
  transcription of genes to make RNA occurs, organelles duplicate
  protein synthesis including making enzymes for DNA

Question 8

Checkpoint 1

Answer 8

• Between G1/S = halts progress into S phase if DNA’s damaged
• -> repairs damage + triggers apoptosis if severe

Question 9

P53 gene

Answer 9

Involved in Checkpoint between G1/S
Makes P53 protein that checks DNA + is a tumour suppressor
If mutated, uncontrollable division is more likely

Question 10

S phase

Answer 10

• Synthesis of DNA - chromosomes unwound and DNA replicated
• When all chromosomes have been duplicated, each consists of a pair of identical sister chromatids
• Phase is rapid as base pairs are exposed to mutagenic agents –> reducing spontaneous mutations

Question 11

G2 phase

Answer 11

• Gap 2 phase - special chemicals ensure that cell is ready for mitosis by stimulating proteins
• -> involved in making chromosomes + forming spindle fibres

Question 12

Checkpoint 2

Answer 12

• Between G2/M - proto-oncogene control cell cycle

Question 13

Interphase

Answer 13

(1st stage of mitosis)
Cell is actively synthesising proteins
Chromosome invisible
Prior to mitosis –> DNA replication

Question 14

Prophase

Answer 14

(2nd stage of mitosis)
Chromosome become visible
Nuclear envelope disntergrates
Nucleolus disappears

Question 15

Metaphase

Answer 15

(3rd stage of mitosis)
Spindle fibers (made of tubulin - a protein) form
The pair of chromatids line up in centre of cell

Question 16

Anaphase

Answer 16

(4th stage of mitosis)
Spindle fibres attach to chromotids –> contract
Chromotids pulled apart towards the poles

Question 17

Telophase

Answer 17

(5th stage of mitosis)
Chromotids reach poles and become indistinct
Nuclear envelope + nucleolus reforms
Spindles disintergrate