Mitosis and the Cell Cycle

Question 2

What are the 4 stages of mitosis?

Answer 2

Prophase
Metaphase
Anaphase
Telophase

Question 3

What 5 things happen in Prophase?

Answer 3

• the chromatin coils and condenses into chromosomes (2 sister chromatids joined at the centromere)
• nucleolus disintegrates
• nuclear envelope disintegrates
• centrioles move to poles
• centrioles produce spindle fibres

Question 4

What 2 things happen in Metaphase?

Answer 4

• spindle attaches to chromosomes at the centromere
• chromosomes line up along the equator of the cell

Question 5

What 2 things happen in Anaphase?

Answer 5

• chromosomes are separated
• 2 sister chromatids (now called chromosomes) move to opposite poles of the cell

Question 6

What 5 things happen in Telophase?

Answer 6

• chromosomes ‘uncoil’ and turn back into chromatin
• nucleolus reforms
• nuclear envelope reforms
• spindle fibres detach
• spindle fibres disintegrate

Question 7

Why are root cells used when investigating mitosis?

Answer 7

as root cells are growing, mitosis is happening as cells divide

Question 8

Explain how to prepare a sample that can be used to investigate mitosis

Answer 8

• place root tips into HCl for 5 minutes, then rinse with water
• cut small, thin slices of a root
• place on slide and use mounted needle to spread thin layers of cell
• add a few drops of stain (e.g toluidine blue)
• place cover slip on

Question 9

In which stage of the cell cycle is DNA replicated?

Answer 9

S

Question 10

Describe how to calculate the mitotic index

Answer 10

cells undergoing mitosis/total number of cells x100

Question 11

What might a high mitotic index suggest?

Answer 11

tissue repair/growth is occurring; possibly, tumours are developing (especially if in adult cells)

Question 12

What is the name given to the division of cytoplasm?

Answer 12

cytokinesis

Question 13

What is a tumour?

Answer 13

a mass of cells caused by uncontrolled cell division

Question 14

How do cancer treatments work?

Answer 14

they re-establish control over the rate of cell division by disrupting the cell cycle and killing tumour cells

Question 15

Describe binary fission in bacteria

Answer 15

• circular DNA is replicated
• plasmids are replicated
• division of cytoplasm to form daughter cells

Question 16

Suggest and explain how two environmental variables could be changed to increase the growth rate of these cells

Answer 16

• increase in temp -> causes increased enzymes activity
• increase in [glucose] -> increased respiration
• increase in [oxygen] -> increased respiration
• increase in number of nucleotides -> increased DNA synthesis

Question 17

Why would preventing the formation of spindle stop the cell cycle?

Answer 17

• centromeres would not attach to spindle fibres
• cannot be lined up, no metaphases
  OR
• CHROMATIDS could not be separated
• no anaphase

Question 18

What are the 3 stages of the cell cycle?

Answer 18

mitosis, cytokinesis, interphase

Question 19

Why is mitosis/the cell cycle important?

Answer 19

• growth
• repair
• reproduction

Question 20

How do viruses replicate?

Answer 20

they do not undergo cell division, instead they infect host cells, and the host cells replicate viral proteins (and particles) for them

Question 21

What happens in interphase?

Answer 21

cell grows, organelles replicate, DNA replicates, DNA is checked

Question 22

How is mitosis controlled?

Answer 22

2 types of genes that speed up or slow down cell division