3.2.2 mitosis and cell cycle

Question 1

in which cells does the cell cycle occur?

Answer 1

eukaryotic cells.

Question 2

what is the order of the cell cycle?

Answer 2

G1 phase > S phase > G2 phase > cell division

Question 3

what is G1?

Answer 3

growth one, organelle synthesis and protein synthesis.

Question 4

what is the S phase?

Answer 4

is where DNA replication takes place, where the two chromatids are joined at the centre by a centromere = chromosome.

Question 5

what is G2?

Answer 5

growth 2.
preparation for mitosis, making cell bigger.

Question 6

what is the stages of mitosis?

Answer 6

IPMAT:
- interphase.
- prophase.
- metaphase.
- anaphase.
- telophase.

Question 7

what happens in interphase?

Answer 7

DNA isn’t visible as it is tightly coiled. G1, S and G2 have occurred already.

Question 8

what happens in prophase?

Answer 8

• nuclear membrane begins to break down.
• DNA condenses = making chromosomes visible.
• spindle fibres start to form between poles of cell.

Question 9

what happens in metaphase?

Answer 9

• chromosomes line up at the equator of the cell.
• chromosomes attach to spindle fibres by their centromere.

Question 10

what happens in anaphase?

Answer 10

• centromere breaks.
• chromatids separate and move to opposite poles of the cell.
• the spindle fibres contract to pull chromatids apart.

Question 11

what happens in telophase?

Answer 11

• nuclear membrane reforms around each mass of chromosomes and spindle fibres break down.
• chromosomes uncoil = no longer visible.

Question 12

what happens in cytokinesis?

Answer 12

cell membrane and cytoplasm divide to form 2 new cells each containing one nucleus.

Question 13

how to work out mitotic index?

Answer 13

number of cells undergoing mitosis/total number of cells in field of view

Question 14

what checks are done at the end of G1?

Answer 14

• cell size.
• DNA damage.
• nutrients.
• are growth factors present?

Question 15

what checks are done at the end of the S phase?

Answer 15

• is DNA replication complete?
• DNA damage.
  = aptosis will occur if cell cannot be repaired.

Question 16

what checks are done in metaphase?

Answer 16

• are the chromosomes attached correctly to the spindle fibres?

Question 17

what can happen if the cell cycle and cell division is uncontrolled?

Answer 17

cancer.

Question 18

what checkpoint genes stops the cycle when damage is detected?

Answer 18

tumour suppressor genes = disabled and switched off if cancer is present.

Question 19

what stimulates cell division?

Answer 19

proto-oncogenes = switched on and increased in activity when cancer is present.

Question 20

how is cancer treated?

Answer 20

• sometimes involves the blocking of parts of the cell cycle = so cell division and cancer growth stops, disrupting all the cells in the body, mostly rapidly growing cells like hair follicles = common side effect of cancer.